From patchwork Tue Apr 2 15:45:44 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881919 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 59CC313B5 for ; Tue, 2 Apr 2019 15:48:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4102F201F5 for ; Tue, 2 Apr 2019 15:48:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3504F2868C; Tue, 2 Apr 2019 15:48:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9FE57286A1 for ; Tue, 2 Apr 2019 15:48:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730756AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:36870 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728741AbfDBPsd (ORCPT ); Tue, 2 Apr 2019 11:48:33 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 26B282084B; Tue, 2 Apr 2019 15:48:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220111; bh=ZjSxw3zlBruk2UJiNV4BLKhEkdxa5bsRJ71k4n7VlXk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HkHj+53fKuU9e72EfxIQxAINBa9Iu0ZqPupY7wlqpvzs4uvgpNqBSCUXPI9LlzVvo yh5EQg/xtJ/GWV7SkbxZ/SsTmhB3IyDUQjtIROz63FHwB9Q1HAOSiDj38QocjgJQz4 jSbFQaebKQNrVtcZ33wZEHfclSDJ3kCs6FnRR7ko= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 01/17] fs, fscrypt: move uapi definitions to new header Date: Tue, 2 Apr 2019 08:45:44 -0700 Message-Id: <20190402154600.32432-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers More fscrypt definitions are being added, and we shouldn't use a disproportionate amount of space in for fscrypt stuff. So move the fscrypt definitions to a new header . For source compatibility with existing userspace programs, still includes the new header. Signed-off-by: Eric Biggers --- MAINTAINERS | 1 + include/linux/fscrypt.h | 1 + include/uapi/linux/fs.h | 54 ++------------------------------- include/uapi/linux/fscrypt.h | 58 ++++++++++++++++++++++++++++++++++++ 4 files changed, 63 insertions(+), 51 deletions(-) create mode 100644 include/uapi/linux/fscrypt.h diff --git a/MAINTAINERS b/MAINTAINERS index 43b36dbed48e7..3b84bf3bf7cae 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6351,6 +6351,7 @@ T: git git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git S: Supported F: fs/crypto/ F: include/linux/fscrypt*.h +F: include/uapi/linux/fscrypt.h F: Documentation/filesystems/fscrypt.rst FSI-ATTACHED I2C DRIVER diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index e5194fc3983e9..8b1e444214973 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -16,6 +16,7 @@ #include #include #include +#include #define FS_CRYPTO_BLOCK_SIZE 16 diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 121e82ce296b5..0f4e66b1bcd09 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -13,6 +13,9 @@ #include #include #include +#ifndef __KERNEL__ +#include +#endif /* Use of MS_* flags within the kernel is restricted to core mount(2) code. */ #if !defined(__KERNEL__) @@ -212,57 +215,6 @@ struct fsxattr { #define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX]) #define FS_IOC_SETFSLABEL _IOW(0x94, 50, char[FSLABEL_MAX]) -/* - * File system encryption support - */ -/* Policy provided via an ioctl on the topmost directory */ -#define FS_KEY_DESCRIPTOR_SIZE 8 - -#define FS_POLICY_FLAGS_PAD_4 0x00 -#define FS_POLICY_FLAGS_PAD_8 0x01 -#define FS_POLICY_FLAGS_PAD_16 0x02 -#define FS_POLICY_FLAGS_PAD_32 0x03 -#define FS_POLICY_FLAGS_PAD_MASK 0x03 -#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */ -#define FS_POLICY_FLAGS_VALID 0x07 - -/* Encryption algorithms */ -#define FS_ENCRYPTION_MODE_INVALID 0 -#define FS_ENCRYPTION_MODE_AES_256_XTS 1 -#define FS_ENCRYPTION_MODE_AES_256_GCM 2 -#define FS_ENCRYPTION_MODE_AES_256_CBC 3 -#define FS_ENCRYPTION_MODE_AES_256_CTS 4 -#define FS_ENCRYPTION_MODE_AES_128_CBC 5 -#define FS_ENCRYPTION_MODE_AES_128_CTS 6 -#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* Removed, do not use. */ -#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* Removed, do not use. */ -#define FS_ENCRYPTION_MODE_ADIANTUM 9 - -struct fscrypt_policy { - __u8 version; - __u8 contents_encryption_mode; - __u8 filenames_encryption_mode; - __u8 flags; - __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; -}; - -#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) -#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) -#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) - -/* Parameters for passing an encryption key into the kernel keyring */ -#define FS_KEY_DESC_PREFIX "fscrypt:" -#define FS_KEY_DESC_PREFIX_SIZE 8 - -/* Structure that userspace passes to the kernel keyring */ -#define FS_MAX_KEY_SIZE 64 - -struct fscrypt_key { - __u32 mode; - __u8 raw[FS_MAX_KEY_SIZE]; - __u32 size; -}; - /* * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS) * diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h new file mode 100644 index 0000000000000..193339cb53fdb --- /dev/null +++ b/include/uapi/linux/fscrypt.h @@ -0,0 +1,58 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_FSCRYPT_H +#define _UAPI_LINUX_FSCRYPT_H + +#include + +/* + * File system encryption support + */ +/* Policy provided via an ioctl on the topmost directory */ +#define FS_KEY_DESCRIPTOR_SIZE 8 + +#define FS_POLICY_FLAGS_PAD_4 0x00 +#define FS_POLICY_FLAGS_PAD_8 0x01 +#define FS_POLICY_FLAGS_PAD_16 0x02 +#define FS_POLICY_FLAGS_PAD_32 0x03 +#define FS_POLICY_FLAGS_PAD_MASK 0x03 +#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */ +#define FS_POLICY_FLAGS_VALID 0x07 + +/* Encryption algorithms */ +#define FS_ENCRYPTION_MODE_INVALID 0 +#define FS_ENCRYPTION_MODE_AES_256_XTS 1 +#define FS_ENCRYPTION_MODE_AES_256_GCM 2 +#define FS_ENCRYPTION_MODE_AES_256_CBC 3 +#define FS_ENCRYPTION_MODE_AES_256_CTS 4 +#define FS_ENCRYPTION_MODE_AES_128_CBC 5 +#define FS_ENCRYPTION_MODE_AES_128_CTS 6 +#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* Removed, do not use. */ +#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* Removed, do not use. */ +#define FS_ENCRYPTION_MODE_ADIANTUM 9 + +struct fscrypt_policy { + __u8 version; + __u8 contents_encryption_mode; + __u8 filenames_encryption_mode; + __u8 flags; + __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; +}; + +#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) +#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) +#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) + +/* Parameters for passing an encryption key into the kernel keyring */ +#define FS_KEY_DESC_PREFIX "fscrypt:" +#define FS_KEY_DESC_PREFIX_SIZE 8 + +/* Structure that userspace passes to the kernel keyring */ +#define FS_MAX_KEY_SIZE 64 + +struct fscrypt_key { + __u32 mode; + __u8 raw[FS_MAX_KEY_SIZE]; + __u32 size; +}; + +#endif /* _UAPI_LINUX_FSCRYPT_H */ From patchwork Tue Apr 2 15:45:45 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881969 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3145D184E for ; Tue, 2 Apr 2019 15:49:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 23364201F5 for ; Tue, 2 Apr 2019 15:49:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1783A286A1; Tue, 2 Apr 2019 15:49:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5B13F201F5 for ; Tue, 2 Apr 2019 15:49:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731363AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:36926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730553AbfDBPsd (ORCPT ); Tue, 2 Apr 2019 11:48:33 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9BE522084C; Tue, 2 Apr 2019 15:48:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220111; bh=KYLtfSd0mHwK6AioWXu+8Gh7pj2P2gQwwQn9p1VE2b8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P1FqLrrSJssatZNZVRaikqY7FPyWeRga3AlgCAZrfJqv37071aHXSpC5mQ9PqmYmU OrNHbVIPB0Fglc4CK/b78k7XP+munzYrqAQPIn4JZ/zriAoAZAZmDavtVLfSqW3GOx qYJWPybJBt1wAsSGyCVIGowTa6FDYFYTyU9z+eto= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 02/17] fscrypt: use FSCRYPT_ prefix for uapi constants Date: Tue, 2 Apr 2019 08:45:45 -0700 Message-Id: <20190402154600.32432-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Prefix all filesystem encryption UAPI constants except the ioctl numbers with "FSCRYPT_" rather than with "FS_". This namespaces the constants more appropriately and makes it clear that they are related specifically to the filesystem encryption feature, and to the 'fscrypt_*' structures. With some of the old names like "FS_POLICY_FLAGS_VALID", it was not immediately clear that the constant had anything to do with encryption. This is also useful because we'll be adding more encryption-related constants, e.g. for the policy version, and we'd otherwise have to choose whether to use unclear names like FS_POLICY_V1 or inconsistent names like FS_ENCRYPTION_POLICY_V1. For source compatibility with existing userspace programs, keep the old names defined as aliases to the new names. Finally, as long as new names are being defined anyway, I skipped defining new names for the fscrypt mode numbers that aren't actually used: INVALID (0), AES_256_GCM (2), AES_256_CBC (3), SPECK128_256_XTS (7), and SPECK128_256_CTS (8). Signed-off-by: Eric Biggers --- Documentation/filesystems/fscrypt.rst | 36 +++++++-------- include/uapi/linux/fscrypt.h | 66 +++++++++++++++++---------- 2 files changed, 61 insertions(+), 41 deletions(-) diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 08c23b60e0164..4f9df6ba669e5 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -223,9 +223,10 @@ a little endian number, except that: is encrypted with AES-256 where the AES-256 key is the SHA-256 hash of the file's data encryption key. -- In the "direct key" configuration (FS_POLICY_FLAG_DIRECT_KEY set in - the fscrypt_policy), the file's nonce is also appended to the IV. - Currently this is only allowed with the Adiantum encryption mode. +- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY + set in the fscrypt_policy), the file's nonce is also appended to the + IV. Currently this is only allowed with the Adiantum encryption + mode. Filenames encryption -------------------- @@ -272,14 +273,14 @@ empty directory or verifies that a directory or regular file already has the specified encryption policy. It takes in a pointer to a :c:type:`struct fscrypt_policy`, defined as follows:: - #define FS_KEY_DESCRIPTOR_SIZE 8 + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 struct fscrypt_policy { __u8 version; __u8 contents_encryption_mode; __u8 filenames_encryption_mode; __u8 flags; - __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; }; This structure must be initialized as follows: @@ -288,18 +289,17 @@ This structure must be initialized as follows: - ``contents_encryption_mode`` and ``filenames_encryption_mode`` must be set to constants from ```` which identify the - encryption modes to use. If unsure, use - FS_ENCRYPTION_MODE_AES_256_XTS (1) for ``contents_encryption_mode`` - and FS_ENCRYPTION_MODE_AES_256_CTS (4) for - ``filenames_encryption_mode``. + encryption modes to use. If unsure, use FSCRYPT_MODE_AES_256_XTS + (1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS + (4) for ``filenames_encryption_mode``. - ``flags`` must contain a value from ```` which identifies the amount of NUL-padding to use when encrypting - filenames. If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3). - In addition, if the chosen encryption modes are both - FS_ENCRYPTION_MODE_ADIANTUM, this can contain - FS_POLICY_FLAG_DIRECT_KEY to specify that the master key should be - used directly, without key derivation. + filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3). In + addition, if the chosen encryption modes are both + FSCRYPT_MODE_ADIANTUM, this can contain + FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should + be used directly, without key derivation. - ``master_key_descriptor`` specifies how to find the master key in the keyring; see `Adding keys`_. It is up to userspace to choose a @@ -399,11 +399,11 @@ followed by the 16-character lower case hex representation of the ``master_key_descriptor`` that was set in the encryption policy. The key payload must conform to the following structure:: - #define FS_MAX_KEY_SIZE 64 + #define FSCRYPT_MAX_KEY_SIZE 64 struct fscrypt_key { u32 mode; - u8 raw[FS_MAX_KEY_SIZE]; + u8 raw[FSCRYPT_MAX_KEY_SIZE]; u32 size; }; @@ -572,7 +572,7 @@ much confusion if an encryption policy were to be added to or removed from anything other than an empty directory.) The struct is defined as follows:: - #define FS_KEY_DESCRIPTOR_SIZE 8 + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 #define FS_KEY_DERIVATION_NONCE_SIZE 16 struct fscrypt_context { @@ -580,7 +580,7 @@ as follows:: u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; - u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 193339cb53fdb..f9b99cc028bc6 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -8,34 +8,30 @@ * File system encryption support */ /* Policy provided via an ioctl on the topmost directory */ -#define FS_KEY_DESCRIPTOR_SIZE 8 +#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 -#define FS_POLICY_FLAGS_PAD_4 0x00 -#define FS_POLICY_FLAGS_PAD_8 0x01 -#define FS_POLICY_FLAGS_PAD_16 0x02 -#define FS_POLICY_FLAGS_PAD_32 0x03 -#define FS_POLICY_FLAGS_PAD_MASK 0x03 -#define FS_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */ -#define FS_POLICY_FLAGS_VALID 0x07 +/* Encryption policy flags */ +#define FSCRYPT_POLICY_FLAGS_PAD_4 0x00 +#define FSCRYPT_POLICY_FLAGS_PAD_8 0x01 +#define FSCRYPT_POLICY_FLAGS_PAD_16 0x02 +#define FSCRYPT_POLICY_FLAGS_PAD_32 0x03 +#define FSCRYPT_POLICY_FLAGS_PAD_MASK 0x03 +#define FSCRYPT_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */ +#define FSCRYPT_POLICY_FLAGS_VALID 0x07 /* Encryption algorithms */ -#define FS_ENCRYPTION_MODE_INVALID 0 -#define FS_ENCRYPTION_MODE_AES_256_XTS 1 -#define FS_ENCRYPTION_MODE_AES_256_GCM 2 -#define FS_ENCRYPTION_MODE_AES_256_CBC 3 -#define FS_ENCRYPTION_MODE_AES_256_CTS 4 -#define FS_ENCRYPTION_MODE_AES_128_CBC 5 -#define FS_ENCRYPTION_MODE_AES_128_CTS 6 -#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* Removed, do not use. */ -#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* Removed, do not use. */ -#define FS_ENCRYPTION_MODE_ADIANTUM 9 +#define FSCRYPT_MODE_AES_256_XTS 1 +#define FSCRYPT_MODE_AES_256_CTS 4 +#define FSCRYPT_MODE_AES_128_CBC 5 +#define FSCRYPT_MODE_AES_128_CTS 6 +#define FSCRYPT_MODE_ADIANTUM 9 struct fscrypt_policy { __u8 version; __u8 contents_encryption_mode; __u8 filenames_encryption_mode; __u8 flags; - __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; }; #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) @@ -43,16 +39,40 @@ struct fscrypt_policy { #define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) /* Parameters for passing an encryption key into the kernel keyring */ -#define FS_KEY_DESC_PREFIX "fscrypt:" -#define FS_KEY_DESC_PREFIX_SIZE 8 +#define FSCRYPT_KEY_DESC_PREFIX "fscrypt:" +#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8 /* Structure that userspace passes to the kernel keyring */ -#define FS_MAX_KEY_SIZE 64 +#define FSCRYPT_MAX_KEY_SIZE 64 struct fscrypt_key { __u32 mode; - __u8 raw[FS_MAX_KEY_SIZE]; + __u8 raw[FSCRYPT_MAX_KEY_SIZE]; __u32 size; }; +/**********************************************************************/ + +/* old names; don't add anything new here! */ +#define FS_KEY_DESCRIPTOR_SIZE FSCRYPT_KEY_DESCRIPTOR_SIZE +#define FS_POLICY_FLAGS_PAD_4 FSCRYPT_POLICY_FLAGS_PAD_4 +#define FS_POLICY_FLAGS_PAD_8 FSCRYPT_POLICY_FLAGS_PAD_8 +#define FS_POLICY_FLAGS_PAD_16 FSCRYPT_POLICY_FLAGS_PAD_16 +#define FS_POLICY_FLAGS_PAD_32 FSCRYPT_POLICY_FLAGS_PAD_32 +#define FS_POLICY_FLAGS_PAD_MASK FSCRYPT_POLICY_FLAGS_PAD_MASK +#define FS_POLICY_FLAG_DIRECT_KEY FSCRYPT_POLICY_FLAG_DIRECT_KEY +#define FS_POLICY_FLAGS_VALID FSCRYPT_POLICY_FLAGS_VALID +#define FS_ENCRYPTION_MODE_INVALID 0 /* never used */ +#define FS_ENCRYPTION_MODE_AES_256_XTS FSCRYPT_MODE_AES_256_XTS +#define FS_ENCRYPTION_MODE_AES_256_GCM 2 /* never used */ +#define FS_ENCRYPTION_MODE_AES_256_CBC 3 /* never used */ +#define FS_ENCRYPTION_MODE_AES_256_CTS FSCRYPT_MODE_AES_256_CTS +#define FS_ENCRYPTION_MODE_AES_128_CBC FSCRYPT_MODE_AES_128_CBC +#define FS_ENCRYPTION_MODE_AES_128_CTS FSCRYPT_MODE_AES_128_CTS +#define FS_ENCRYPTION_MODE_SPECK128_256_XTS 7 /* removed */ +#define FS_ENCRYPTION_MODE_SPECK128_256_CTS 8 /* removed */ +#define FS_ENCRYPTION_MODE_ADIANTUM FSCRYPT_MODE_ADIANTUM +#define FS_KEY_DESC_PREFIX FSCRYPT_KEY_DESC_PREFIX +#define FS_KEY_DESC_PREFIX_SIZE FSCRYPT_KEY_DESC_PREFIX_SIZE +#define FS_MAX_KEY_SIZE FSCRYPT_MAX_KEY_SIZE #endif /* _UAPI_LINUX_FSCRYPT_H */ From patchwork Tue Apr 2 15:45:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10882011 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4A6C51800 for ; Tue, 2 Apr 2019 15:49:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3C4BB201F5 for ; Tue, 2 Apr 2019 15:49:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 30447287FE; Tue, 2 Apr 2019 15:49:27 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 568EB201F5 for ; Tue, 2 Apr 2019 15:49:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731675AbfDBPtZ (ORCPT ); Tue, 2 Apr 2019 11:49:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:36884 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730854AbfDBPsd (ORCPT ); Tue, 2 Apr 2019 11:48:33 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1953D2147A; Tue, 2 Apr 2019 15:48:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220112; bh=mpqj1MEyKDy9xPTMgzuJSST5mVu+w5BsNQMNbMEcKrw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IM+PlL+tsoANxfLb3zp6lZtqsANMxhPP8n6MzwACZx8YijfqToiG21w01qosI0RRw 26TP8MzkKDY2EYVbmbvf2biis9Bfl8QtjnoI75Rj3vSIRTATl183mZQPwlnzMle1dR 83q28wJSvQj06cBhf8zn78lY6utNGrPY2a2jY+LE= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 03/17] fscrypt: use FSCRYPT_* definitions, not FS_* Date: Tue, 2 Apr 2019 08:45:46 -0700 Message-Id: <20190402154600.32432-4-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Update fs/crypto/ to use the new names for the UAPI constants rather than the old names, then make the old definitions conditional on !__KERNEL__. Signed-off-by: Eric Biggers --- fs/crypto/crypto.c | 2 +- fs/crypto/fname.c | 2 +- fs/crypto/fscrypt_private.h | 16 +++++------ fs/crypto/keyinfo.c | 53 ++++++++++++++++++------------------ fs/crypto/policy.c | 14 +++++----- include/uapi/linux/fscrypt.h | 2 ++ 6 files changed, 46 insertions(+), 43 deletions(-) diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 4dc788e3bc96b..8217a44346215 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -139,7 +139,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, memset(iv, 0, ci->ci_mode->ivsize); iv->lblk_num = cpu_to_le64(lblk_num); - if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) + if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE); if (ci->ci_essiv_tfm != NULL) diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 7ff40a73dbece..37c26ad36d0e3 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -187,7 +187,7 @@ bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret) { int padding = 4 << (inode->i_crypt_info->ci_flags & - FS_POLICY_FLAGS_PAD_MASK); + FSCRYPT_POLICY_FLAGS_PAD_MASK); u32 encrypted_len; if (orig_len > max_len) diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 7da2761595933..52e09ef40bfa6 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -34,7 +34,7 @@ struct fscrypt_context { u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; - u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; } __packed; @@ -84,7 +84,7 @@ struct fscrypt_info { u8 ci_data_mode; u8 ci_filename_mode; u8 ci_flags; - u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + u8 ci_master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; @@ -99,16 +99,16 @@ typedef enum { static inline bool fscrypt_valid_enc_modes(u32 contents_mode, u32 filenames_mode) { - if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC && - filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS) + if (contents_mode == FSCRYPT_MODE_AES_128_CBC && + filenames_mode == FSCRYPT_MODE_AES_128_CTS) return true; - if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS && - filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS) + if (contents_mode == FSCRYPT_MODE_AES_256_XTS && + filenames_mode == FSCRYPT_MODE_AES_256_CTS) return true; - if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM && - filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM) + if (contents_mode == FSCRYPT_MODE_ADIANTUM && + filenames_mode == FSCRYPT_MODE_ADIANTUM) return true; return false; diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 322ce9686bdba..058e2e0fda430 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -21,7 +21,7 @@ static struct crypto_shash *essiv_hash_tfm; -/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */ +/* Table of keys referenced by DIRECT_KEY policies */ static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */ static DEFINE_SPINLOCK(fscrypt_master_keys_lock); @@ -78,7 +78,7 @@ static int derive_key_aes(const u8 *master_key, */ static struct key * find_and_lock_process_key(const char *prefix, - const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE], + const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], unsigned int min_keysize, const struct fscrypt_key **payload_ret) { @@ -88,7 +88,7 @@ find_and_lock_process_key(const char *prefix, const struct fscrypt_key *payload; description = kasprintf(GFP_NOFS, "%s%*phN", prefix, - FS_KEY_DESCRIPTOR_SIZE, descriptor); + FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); if (!description) return ERR_PTR(-ENOMEM); @@ -106,7 +106,7 @@ find_and_lock_process_key(const char *prefix, payload = (const struct fscrypt_key *)ukp->data; if (ukp->datalen != sizeof(struct fscrypt_key) || - payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) { + payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { fscrypt_warn(NULL, "key with description '%s' has invalid payload", key->description); @@ -130,32 +130,32 @@ find_and_lock_process_key(const char *prefix, } static struct fscrypt_mode available_modes[] = { - [FS_ENCRYPTION_MODE_AES_256_XTS] = { + [FSCRYPT_MODE_AES_256_XTS] = { .friendly_name = "AES-256-XTS", .cipher_str = "xts(aes)", .keysize = 64, .ivsize = 16, }, - [FS_ENCRYPTION_MODE_AES_256_CTS] = { + [FSCRYPT_MODE_AES_256_CTS] = { .friendly_name = "AES-256-CTS-CBC", .cipher_str = "cts(cbc(aes))", .keysize = 32, .ivsize = 16, }, - [FS_ENCRYPTION_MODE_AES_128_CBC] = { + [FSCRYPT_MODE_AES_128_CBC] = { .friendly_name = "AES-128-CBC", .cipher_str = "cbc(aes)", .keysize = 16, .ivsize = 16, .needs_essiv = true, }, - [FS_ENCRYPTION_MODE_AES_128_CTS] = { + [FSCRYPT_MODE_AES_128_CTS] = { .friendly_name = "AES-128-CTS-CBC", .cipher_str = "cts(cbc(aes))", .keysize = 16, .ivsize = 16, }, - [FS_ENCRYPTION_MODE_ADIANTUM] = { + [FSCRYPT_MODE_ADIANTUM] = { .friendly_name = "Adiantum", .cipher_str = "adiantum(xchacha12,aes)", .keysize = 32, @@ -194,7 +194,7 @@ static int find_and_derive_key(const struct inode *inode, const struct fscrypt_key *payload; int err; - key = find_and_lock_process_key(FS_KEY_DESC_PREFIX, + key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, ctx->master_key_descriptor, mode->keysize, &payload); if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) { @@ -205,7 +205,7 @@ static int find_and_derive_key(const struct inode *inode, if (IS_ERR(key)) return PTR_ERR(key); - if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) { + if (ctx->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) { fscrypt_warn(inode->i_sb, "direct key mode not allowed with %s", @@ -269,14 +269,14 @@ allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key, return ERR_PTR(err); } -/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */ +/* Master key referenced by DIRECT_KEY policy */ struct fscrypt_master_key { struct hlist_node mk_node; refcount_t mk_refcount; const struct fscrypt_mode *mk_mode; struct crypto_skcipher *mk_ctfm; - u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE]; - u8 mk_raw[FS_MAX_KEY_SIZE]; + u8 mk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + u8 mk_raw[FSCRYPT_MAX_KEY_SIZE]; }; static void free_master_key(struct fscrypt_master_key *mk) @@ -317,13 +317,13 @@ find_or_insert_master_key(struct fscrypt_master_key *to_insert, * raw key, and use crypto_memneq() when comparing raw keys. */ - BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE); + BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); spin_lock(&fscrypt_master_keys_lock); hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) { if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor, - FS_KEY_DESCRIPTOR_SIZE) != 0) + FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) continue; if (mode != mk->mk_mode) continue; @@ -367,7 +367,7 @@ fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, goto err_free_mk; } memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + FSCRYPT_KEY_DESCRIPTOR_SIZE); memcpy(mk->mk_raw, raw_key, mode->keysize); return find_or_insert_master_key(mk, raw_key, mode, ci); @@ -446,8 +446,8 @@ void __exit fscrypt_essiv_cleanup(void) /* * Given the encryption mode and key (normally the derived key, but for - * FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's - * symmetric cipher transform object(s). + * DIRECT_KEY mode it's the master key), set up the inode's symmetric cipher + * transform object(s). */ static int setup_crypto_transform(struct fscrypt_info *ci, struct fscrypt_mode *mode, @@ -457,7 +457,7 @@ static int setup_crypto_transform(struct fscrypt_info *ci, struct crypto_skcipher *ctfm; int err; - if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) { + if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { mk = fscrypt_get_master_key(ci, mode, raw_key, inode); if (IS_ERR(mk)) return PTR_ERR(mk); @@ -474,7 +474,7 @@ static int setup_crypto_transform(struct fscrypt_info *ci, if (mode->needs_essiv) { /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ WARN_ON(mode->ivsize != AES_BLOCK_SIZE); - WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY); + WARN_ON(ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY); err = init_essiv_generator(ci, raw_key, mode->keysize); if (err) { @@ -524,9 +524,10 @@ int fscrypt_get_encryption_info(struct inode *inode) /* Fake up a context for an unencrypted directory */ memset(&ctx, 0, sizeof(ctx)); ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE); + ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.master_key_descriptor, 0x42, + FSCRYPT_KEY_DESCRIPTOR_SIZE); } else if (res != sizeof(ctx)) { return -EINVAL; } @@ -534,7 +535,7 @@ int fscrypt_get_encryption_info(struct inode *inode) if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) return -EINVAL; - if (ctx.flags & ~FS_POLICY_FLAGS_VALID) + if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) return -EINVAL; crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); @@ -545,7 +546,7 @@ int fscrypt_get_encryption_info(struct inode *inode) crypt_info->ci_data_mode = ctx.contents_encryption_mode; crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + FSCRYPT_KEY_DESCRIPTOR_SIZE); memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); mode = select_encryption_mode(crypt_info, inode); diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index bd7eaf9b3f003..1e0563cea1a56 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -22,7 +22,7 @@ static bool is_encryption_context_consistent_with_policy( const struct fscrypt_policy *policy) { return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && + FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && (ctx->flags == policy->flags) && (ctx->contents_encryption_mode == policy->contents_encryption_mode) && @@ -37,13 +37,13 @@ static int create_encryption_context_from_policy(struct inode *inode, ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + FSCRYPT_KEY_DESCRIPTOR_SIZE); if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, policy->filenames_encryption_mode)) return -EINVAL; - if (policy->flags & ~FS_POLICY_FLAGS_VALID) + if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) return -EINVAL; ctx.contents_encryption_mode = policy->contents_encryption_mode; @@ -126,7 +126,7 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) policy.filenames_encryption_mode = ctx.filenames_encryption_mode; policy.flags = ctx.flags; memcpy(policy.master_key_descriptor, ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + FSCRYPT_KEY_DESCRIPTOR_SIZE); if (copy_to_user(arg, &policy, sizeof(policy))) return -EFAULT; @@ -200,7 +200,7 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) if (parent_ci && child_ci) { return memcmp(parent_ci->ci_master_key_descriptor, child_ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && + FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && (parent_ci->ci_data_mode == child_ci->ci_data_mode) && (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) && @@ -217,7 +217,7 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) return memcmp(parent_ctx.master_key_descriptor, child_ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && + FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && (parent_ctx.contents_encryption_mode == child_ctx.contents_encryption_mode) && (parent_ctx.filenames_encryption_mode == @@ -255,7 +255,7 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, ctx.filenames_encryption_mode = ci->ci_filename_mode; ctx.flags = ci->ci_flags; memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + FSCRYPT_KEY_DESCRIPTOR_SIZE); get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE); res = parent->i_sb->s_cop->set_context(child, &ctx, diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index f9b99cc028bc6..3bbc5dfbde211 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -53,6 +53,7 @@ struct fscrypt_key { /**********************************************************************/ /* old names; don't add anything new here! */ +#ifndef __KERNEL__ #define FS_KEY_DESCRIPTOR_SIZE FSCRYPT_KEY_DESCRIPTOR_SIZE #define FS_POLICY_FLAGS_PAD_4 FSCRYPT_POLICY_FLAGS_PAD_4 #define FS_POLICY_FLAGS_PAD_8 FSCRYPT_POLICY_FLAGS_PAD_8 @@ -74,5 +75,6 @@ struct fscrypt_key { #define FS_KEY_DESC_PREFIX FSCRYPT_KEY_DESC_PREFIX #define FS_KEY_DESC_PREFIX_SIZE FSCRYPT_KEY_DESC_PREFIX_SIZE #define FS_MAX_KEY_SIZE FSCRYPT_MAX_KEY_SIZE +#endif /* !__KERNEL__ */ #endif /* _UAPI_LINUX_FSCRYPT_H */ From patchwork Tue Apr 2 15:45:47 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881929 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 40D2F184E for ; Tue, 2 Apr 2019 15:48:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 32CBF201F5 for ; Tue, 2 Apr 2019 15:48:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 26C5428691; Tue, 2 Apr 2019 15:48:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D34C6201F5 for ; Tue, 2 Apr 2019 15:48:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731393AbfDBPsj (ORCPT ); Tue, 2 Apr 2019 11:48:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:36964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726582AbfDBPsd (ORCPT ); Tue, 2 Apr 2019 11:48:33 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 955792133D; Tue, 2 Apr 2019 15:48:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220112; bh=m6x57ZiDXqV2W7dMJhnPN12FN8cd+uR7GaniGWjkMyw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0OU/3KKV5WZl8OtSW32Tx4N/NfbqtJROsulpDn25tSGPXxzLv01yTtYJs5yl3qljr 0eYyYWl/B0D8Geo74s6U/bbSFYk0DZRlNZD6ar66b/mk8SL3ONcUstLmiQ8NEyT0U5 acFIxhDxIPLlGU0/LiWBInTMBlNeMgr7I9OWFvdo= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 04/17] fscrypt: add ->ci_inode to fscrypt_info Date: Tue, 2 Apr 2019 08:45:47 -0700 Message-Id: <20190402154600.32432-5-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add an inode back-pointer to 'struct fscrypt_info', such that inode->i_crypt_info->ci_inode == inode. This will be useful for: 1. Evicting the inodes when a fscrypt key is removed, since we'll track the inodes using a given key by linking their fscrypt_infos together, rather than the inodes directly. This avoids bloating 'struct inode' with a new list_head. 2. Simplifying the per-file key setup, since the inode pointer won't have to be passed around everywhere just in case something goes wrong and it's needed for fscrypt_warn(). Signed-off-by: Eric Biggers --- fs/crypto/fscrypt_private.h | 3 +++ fs/crypto/keyinfo.c | 2 ++ 2 files changed, 5 insertions(+) diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 52e09ef40bfa6..ac24edfc297f1 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -73,6 +73,9 @@ struct fscrypt_info { */ struct fscrypt_mode *ci_mode; + /* Back-pointer to the inode */ + struct inode *ci_inode; + /* * If non-NULL, then this inode uses a master key directly rather than a * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm. diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 058e2e0fda430..148a54fb556a6 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -542,6 +542,8 @@ int fscrypt_get_encryption_info(struct inode *inode) if (!crypt_info) return -ENOMEM; + crypt_info->ci_inode = inode; + crypt_info->ci_flags = ctx.flags; crypt_info->ci_data_mode = ctx.contents_encryption_mode; crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; From patchwork Tue Apr 2 15:45:48 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881997 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0827115AC for ; Tue, 2 Apr 2019 15:49:21 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EC58A201F5 for ; Tue, 2 Apr 2019 15:49:20 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DFFFF2868C; Tue, 2 Apr 2019 15:49:20 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E525E27F90 for ; Tue, 2 Apr 2019 15:49:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731229AbfDBPtO (ORCPT ); Tue, 2 Apr 2019 11:49:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:36992 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728678AbfDBPsg (ORCPT ); Tue, 2 Apr 2019 11:48:36 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1380C21473; Tue, 2 Apr 2019 15:48:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220113; bh=4vIA009UF7jm5DSb+jNw1vhA/NpvcPY3oiQoqgg9iRo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a/DH4Qmku715caqe6Hf562CPfvc0anX/01q/SglMz+j70lSbCqniCmKgo2NeBvFAM Y25lQqKi3ucWDubWLxFuA00vzK0bhYL0NPIwNYLt7Wbq9rnMFUCcxROI6zTtjta3ky Qkw/5Ry6NiB3avVvw3aaLNwsivL5xg1xi6BIjFj4= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 05/17] fscrypt: refactor v1 policy key setup into keysetup_legacy.c Date: Tue, 2 Apr 2019 08:45:48 -0700 Message-Id: <20190402154600.32432-6-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers In preparation for introducing v2 encryption policies which will find and derive encryption keys differently from the current v1 encryption policies, refactor the v1 policy-specific key setup code from keyinfo.c into keysetup_legacy.c. Then rename keyinfo.c to keysetup.c. Note: the code moved into keysetup_legacy.c includes the table of master keys referenced by v1 DIRECT_KEY policies. I've chosen to keep this table as-is rather than trying to replace it with using the filesystem-level keyring, since the latter would add more complexity than it would save especially given the requirement to continue to support the keys actually being provided in a process-subscribed keyring. However, to distinguish the structures in this table from the structures that will go in the filesystem-level keyring, I renamed them from 'struct fscrypt_master_key' to 'struct fscrypt_direct_key'. Signed-off-by: Eric Biggers --- fs/crypto/Makefile | 8 +- fs/crypto/fscrypt_private.h | 37 ++- fs/crypto/keyinfo.c | 595 ------------------------------------ fs/crypto/keysetup.c | 309 +++++++++++++++++++ fs/crypto/keysetup_legacy.c | 338 ++++++++++++++++++++ include/linux/fscrypt.h | 4 +- 6 files changed, 685 insertions(+), 606 deletions(-) delete mode 100644 fs/crypto/keyinfo.c create mode 100644 fs/crypto/keysetup.c create mode 100644 fs/crypto/keysetup_legacy.c diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile index cb496989a6b69..75c0c29fcc627 100644 --- a/fs/crypto/Makefile +++ b/fs/crypto/Makefile @@ -1,4 +1,10 @@ obj-$(CONFIG_FS_ENCRYPTION) += fscrypto.o -fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o +fscrypto-y := crypto.o \ + fname.o \ + hooks.o \ + keysetup.o \ + keysetup_legacy.o \ + policy.o + fscrypto-$(CONFIG_BLOCK) += bio.o diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index ac24edfc297f1..c5a8181fc26c1 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -4,9 +4,8 @@ * * Copyright (C) 2015, Google, Inc. * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. */ #ifndef _FSCRYPT_PRIVATE_H @@ -77,11 +76,10 @@ struct fscrypt_info { struct inode *ci_inode; /* - * If non-NULL, then this inode uses a master key directly rather than a - * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm. - * Otherwise, this inode uses a derived key. + * If non-NULL, then encryption is done using the master key directly + * and ci_ctfm will equal ci_direct_key->dk_ctfm. */ - struct fscrypt_master_key *ci_master_key; + struct fscrypt_direct_key *ci_direct_key; /* fields from the fscrypt_context */ u8 ci_data_mode; @@ -161,7 +159,7 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); -/* keyinfo.c */ +/* keysetup.c */ struct fscrypt_mode { const char *friendly_name; @@ -172,6 +170,29 @@ struct fscrypt_mode { bool needs_essiv; }; +static inline bool +fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode) +{ + return mode->ivsize >= offsetofend(union fscrypt_iv, nonce); +} + +extern struct crypto_skcipher * +fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, + const struct inode *inode); + +extern int fscrypt_set_derived_key(struct fscrypt_info *ci, + const u8 *derived_key); + extern void __exit fscrypt_essiv_cleanup(void); +/* keysetup_legacy.c */ + +extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk); + +extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, + const u8 *raw_master_key); + +extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings( + struct fscrypt_info *ci); + #endif /* _FSCRYPT_PRIVATE_H */ diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c deleted file mode 100644 index 148a54fb556a6..0000000000000 --- a/fs/crypto/keyinfo.c +++ /dev/null @@ -1,595 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* - * key management facility for FS encryption support. - * - * Copyright (C) 2015, Google, Inc. - * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. - */ - -#include -#include -#include -#include -#include -#include -#include -#include -#include "fscrypt_private.h" - -static struct crypto_shash *essiv_hash_tfm; - -/* Table of keys referenced by DIRECT_KEY policies */ -static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */ -static DEFINE_SPINLOCK(fscrypt_master_keys_lock); - -/* - * Key derivation function. This generates the derived key by encrypting the - * master key with AES-128-ECB using the inode's nonce as the AES key. - * - * The master key must be at least as long as the derived key. If the master - * key is longer, then only the first 'derived_keysize' bytes are used. - */ -static int derive_key_aes(const u8 *master_key, - const struct fscrypt_context *ctx, - u8 *derived_key, unsigned int derived_keysize) -{ - int res = 0; - struct skcipher_request *req = NULL; - DECLARE_CRYPTO_WAIT(wait); - struct scatterlist src_sg, dst_sg; - struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); - - if (IS_ERR(tfm)) { - res = PTR_ERR(tfm); - tfm = NULL; - goto out; - } - crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); - req = skcipher_request_alloc(tfm, GFP_NOFS); - if (!req) { - res = -ENOMEM; - goto out; - } - skcipher_request_set_callback(req, - CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, - crypto_req_done, &wait); - res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce)); - if (res < 0) - goto out; - - sg_init_one(&src_sg, master_key, derived_keysize); - sg_init_one(&dst_sg, derived_key, derived_keysize); - skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, - NULL); - res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); -out: - skcipher_request_free(req); - crypto_free_skcipher(tfm); - return res; -} - -/* - * Search the current task's subscribed keyrings for a "logon" key with - * description prefix:descriptor, and if found acquire a read lock on it and - * return a pointer to its validated payload in *payload_ret. - */ -static struct key * -find_and_lock_process_key(const char *prefix, - const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], - unsigned int min_keysize, - const struct fscrypt_key **payload_ret) -{ - char *description; - struct key *key; - const struct user_key_payload *ukp; - const struct fscrypt_key *payload; - - description = kasprintf(GFP_NOFS, "%s%*phN", prefix, - FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); - if (!description) - return ERR_PTR(-ENOMEM); - - key = request_key(&key_type_logon, description, NULL); - kfree(description); - if (IS_ERR(key)) - return key; - - down_read(&key->sem); - ukp = user_key_payload_locked(key); - - if (!ukp) /* was the key revoked before we acquired its semaphore? */ - goto invalid; - - payload = (const struct fscrypt_key *)ukp->data; - - if (ukp->datalen != sizeof(struct fscrypt_key) || - payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { - fscrypt_warn(NULL, - "key with description '%s' has invalid payload", - key->description); - goto invalid; - } - - if (payload->size < min_keysize) { - fscrypt_warn(NULL, - "key with description '%s' is too short (got %u bytes, need %u+ bytes)", - key->description, payload->size, min_keysize); - goto invalid; - } - - *payload_ret = payload; - return key; - -invalid: - up_read(&key->sem); - key_put(key); - return ERR_PTR(-ENOKEY); -} - -static struct fscrypt_mode available_modes[] = { - [FSCRYPT_MODE_AES_256_XTS] = { - .friendly_name = "AES-256-XTS", - .cipher_str = "xts(aes)", - .keysize = 64, - .ivsize = 16, - }, - [FSCRYPT_MODE_AES_256_CTS] = { - .friendly_name = "AES-256-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 32, - .ivsize = 16, - }, - [FSCRYPT_MODE_AES_128_CBC] = { - .friendly_name = "AES-128-CBC", - .cipher_str = "cbc(aes)", - .keysize = 16, - .ivsize = 16, - .needs_essiv = true, - }, - [FSCRYPT_MODE_AES_128_CTS] = { - .friendly_name = "AES-128-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 16, - .ivsize = 16, - }, - [FSCRYPT_MODE_ADIANTUM] = { - .friendly_name = "Adiantum", - .cipher_str = "adiantum(xchacha12,aes)", - .keysize = 32, - .ivsize = 32, - }, -}; - -static struct fscrypt_mode * -select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) -{ - if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { - fscrypt_warn(inode->i_sb, - "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", - inode->i_ino, ci->ci_data_mode, - ci->ci_filename_mode); - return ERR_PTR(-EINVAL); - } - - if (S_ISREG(inode->i_mode)) - return &available_modes[ci->ci_data_mode]; - - if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) - return &available_modes[ci->ci_filename_mode]; - - WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", - inode->i_ino, (inode->i_mode & S_IFMT)); - return ERR_PTR(-EINVAL); -} - -/* Find the master key, then derive the inode's actual encryption key */ -static int find_and_derive_key(const struct inode *inode, - const struct fscrypt_context *ctx, - u8 *derived_key, const struct fscrypt_mode *mode) -{ - struct key *key; - const struct fscrypt_key *payload; - int err; - - key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, - ctx->master_key_descriptor, - mode->keysize, &payload); - if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) { - key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix, - ctx->master_key_descriptor, - mode->keysize, &payload); - } - if (IS_ERR(key)) - return PTR_ERR(key); - - if (ctx->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { - if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with %s", - mode->friendly_name); - err = -EINVAL; - } else if (ctx->contents_encryption_mode != - ctx->filenames_encryption_mode) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with different contents and filenames modes"); - err = -EINVAL; - } else { - memcpy(derived_key, payload->raw, mode->keysize); - err = 0; - } - } else { - err = derive_key_aes(payload->raw, ctx, derived_key, - mode->keysize); - } - up_read(&key->sem); - key_put(key); - return err; -} - -/* Allocate and key a symmetric cipher object for the given encryption mode */ -static struct crypto_skcipher * -allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key, - const struct inode *inode) -{ - struct crypto_skcipher *tfm; - int err; - - tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(inode->i_sb, - "error allocating '%s' transform for inode %lu: %ld", - mode->cipher_str, inode->i_ino, PTR_ERR(tfm)); - return tfm; - } - if (unlikely(!mode->logged_impl_name)) { - /* - * fscrypt performance can vary greatly depending on which - * crypto algorithm implementation is used. Help people debug - * performance problems by logging the ->cra_driver_name the - * first time a mode is used. Note that multiple threads can - * race here, but it doesn't really matter. - */ - mode->logged_impl_name = true; - pr_info("fscrypt: %s using implementation \"%s\"\n", - mode->friendly_name, - crypto_skcipher_alg(tfm)->base.cra_driver_name); - } - crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); - err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); - if (err) - goto err_free_tfm; - - return tfm; - -err_free_tfm: - crypto_free_skcipher(tfm); - return ERR_PTR(err); -} - -/* Master key referenced by DIRECT_KEY policy */ -struct fscrypt_master_key { - struct hlist_node mk_node; - refcount_t mk_refcount; - const struct fscrypt_mode *mk_mode; - struct crypto_skcipher *mk_ctfm; - u8 mk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; - u8 mk_raw[FSCRYPT_MAX_KEY_SIZE]; -}; - -static void free_master_key(struct fscrypt_master_key *mk) -{ - if (mk) { - crypto_free_skcipher(mk->mk_ctfm); - kzfree(mk); - } -} - -static void put_master_key(struct fscrypt_master_key *mk) -{ - if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock)) - return; - hash_del(&mk->mk_node); - spin_unlock(&fscrypt_master_keys_lock); - - free_master_key(mk); -} - -/* - * Find/insert the given master key into the fscrypt_master_keys table. If - * found, it is returned with elevated refcount, and 'to_insert' is freed if - * non-NULL. If not found, 'to_insert' is inserted and returned if it's - * non-NULL; otherwise NULL is returned. - */ -static struct fscrypt_master_key * -find_or_insert_master_key(struct fscrypt_master_key *to_insert, - const u8 *raw_key, const struct fscrypt_mode *mode, - const struct fscrypt_info *ci) -{ - unsigned long hash_key; - struct fscrypt_master_key *mk; - - /* - * Careful: to avoid potentially leaking secret key bytes via timing - * information, we must key the hash table by descriptor rather than by - * raw key, and use crypto_memneq() when comparing raw keys. - */ - - BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); - - spin_lock(&fscrypt_master_keys_lock); - hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) { - if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) - continue; - if (mode != mk->mk_mode) - continue; - if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize)) - continue; - /* using existing tfm with same (descriptor, mode, raw_key) */ - refcount_inc(&mk->mk_refcount); - spin_unlock(&fscrypt_master_keys_lock); - free_master_key(to_insert); - return mk; - } - if (to_insert) - hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key); - spin_unlock(&fscrypt_master_keys_lock); - return to_insert; -} - -/* Prepare to encrypt directly using the master key in the given mode */ -static struct fscrypt_master_key * -fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - int err; - - /* Is there already a tfm for this key? */ - mk = find_or_insert_master_key(NULL, raw_key, mode, ci); - if (mk) - return mk; - - /* Nope, allocate one. */ - mk = kzalloc(sizeof(*mk), GFP_NOFS); - if (!mk) - return ERR_PTR(-ENOMEM); - refcount_set(&mk->mk_refcount, 1); - mk->mk_mode = mode; - mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(mk->mk_ctfm)) { - err = PTR_ERR(mk->mk_ctfm); - mk->mk_ctfm = NULL; - goto err_free_mk; - } - memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(mk->mk_raw, raw_key, mode->keysize); - - return find_or_insert_master_key(mk, raw_key, mode, ci); - -err_free_mk: - free_master_key(mk); - return ERR_PTR(err); -} - -static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) -{ - struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); - - /* init hash transform on demand */ - if (unlikely(!tfm)) { - struct crypto_shash *prev_tfm; - - tfm = crypto_alloc_shash("sha256", 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(NULL, - "error allocating SHA-256 transform: %ld", - PTR_ERR(tfm)); - return PTR_ERR(tfm); - } - prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); - if (prev_tfm) { - crypto_free_shash(tfm); - tfm = prev_tfm; - } - } - - { - SHASH_DESC_ON_STACK(desc, tfm); - desc->tfm = tfm; - desc->flags = 0; - - return crypto_shash_digest(desc, key, keysize, salt); - } -} - -static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, - int keysize) -{ - int err; - struct crypto_cipher *essiv_tfm; - u8 salt[SHA256_DIGEST_SIZE]; - - essiv_tfm = crypto_alloc_cipher("aes", 0, 0); - if (IS_ERR(essiv_tfm)) - return PTR_ERR(essiv_tfm); - - ci->ci_essiv_tfm = essiv_tfm; - - err = derive_essiv_salt(raw_key, keysize, salt); - if (err) - goto out; - - /* - * Using SHA256 to derive the salt/key will result in AES-256 being - * used for IV generation. File contents encryption will still use the - * configured keysize (AES-128) nevertheless. - */ - err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); - if (err) - goto out; - -out: - memzero_explicit(salt, sizeof(salt)); - return err; -} - -void __exit fscrypt_essiv_cleanup(void) -{ - crypto_free_shash(essiv_hash_tfm); -} - -/* - * Given the encryption mode and key (normally the derived key, but for - * DIRECT_KEY mode it's the master key), set up the inode's symmetric cipher - * transform object(s). - */ -static int setup_crypto_transform(struct fscrypt_info *ci, - struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - struct crypto_skcipher *ctfm; - int err; - - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { - mk = fscrypt_get_master_key(ci, mode, raw_key, inode); - if (IS_ERR(mk)) - return PTR_ERR(mk); - ctfm = mk->mk_ctfm; - } else { - mk = NULL; - ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(ctfm)) - return PTR_ERR(ctfm); - } - ci->ci_master_key = mk; - ci->ci_ctfm = ctfm; - - if (mode->needs_essiv) { - /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ - WARN_ON(mode->ivsize != AES_BLOCK_SIZE); - WARN_ON(ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY); - - err = init_essiv_generator(ci, raw_key, mode->keysize); - if (err) { - fscrypt_warn(inode->i_sb, - "error initializing ESSIV generator for inode %lu: %d", - inode->i_ino, err); - return err; - } - } - return 0; -} - -static void put_crypt_info(struct fscrypt_info *ci) -{ - if (!ci) - return; - - if (ci->ci_master_key) { - put_master_key(ci->ci_master_key); - } else { - crypto_free_skcipher(ci->ci_ctfm); - crypto_free_cipher(ci->ci_essiv_tfm); - } - kmem_cache_free(fscrypt_info_cachep, ci); -} - -int fscrypt_get_encryption_info(struct inode *inode) -{ - struct fscrypt_info *crypt_info; - struct fscrypt_context ctx; - struct fscrypt_mode *mode; - u8 *raw_key = NULL; - int res; - - if (inode->i_crypt_info) - return 0; - - res = fscrypt_initialize(inode->i_sb->s_cop->flags); - if (res) - return res; - - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0) { - if (!fscrypt_dummy_context_enabled(inode) || - IS_ENCRYPTED(inode)) - return res; - /* Fake up a context for an unencrypted directory */ - memset(&ctx, 0, sizeof(ctx)); - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - } else if (res != sizeof(ctx)) { - return -EINVAL; - } - - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) - return -EINVAL; - - if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) - return -EINVAL; - - crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); - if (!crypt_info) - return -ENOMEM; - - crypt_info->ci_inode = inode; - - crypt_info->ci_flags = ctx.flags; - crypt_info->ci_data_mode = ctx.contents_encryption_mode; - crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; - memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); - - mode = select_encryption_mode(crypt_info, inode); - if (IS_ERR(mode)) { - res = PTR_ERR(mode); - goto out; - } - WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); - crypt_info->ci_mode = mode; - - /* - * This cannot be a stack buffer because it may be passed to the - * scatterlist crypto API as part of key derivation. - */ - res = -ENOMEM; - raw_key = kmalloc(mode->keysize, GFP_NOFS); - if (!raw_key) - goto out; - - res = find_and_derive_key(inode, &ctx, raw_key, mode); - if (res) - goto out; - - res = setup_crypto_transform(crypt_info, mode, raw_key, inode); - if (res) - goto out; - - if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) - crypt_info = NULL; -out: - if (res == -ENOKEY) - res = 0; - put_crypt_info(crypt_info); - kzfree(raw_key); - return res; -} -EXPORT_SYMBOL(fscrypt_get_encryption_info); - -void fscrypt_put_encryption_info(struct inode *inode) -{ - put_crypt_info(inode->i_crypt_info); - inode->i_crypt_info = NULL; -} -EXPORT_SYMBOL(fscrypt_put_encryption_info); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c new file mode 100644 index 0000000000000..829b74974e8f6 --- /dev/null +++ b/fs/crypto/keysetup.c @@ -0,0 +1,309 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup facility for FS encryption support. + * + * Copyright (C) 2015, Google, Inc. + * + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. + */ + +#include +#include +#include +#include + +#include "fscrypt_private.h" + +static struct crypto_shash *essiv_hash_tfm; + +static struct fscrypt_mode available_modes[] = { + [FSCRYPT_MODE_AES_256_XTS] = { + .friendly_name = "AES-256-XTS", + .cipher_str = "xts(aes)", + .keysize = 64, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_256_CTS] = { + .friendly_name = "AES-256-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 32, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_128_CBC] = { + .friendly_name = "AES-128-CBC", + .cipher_str = "cbc(aes)", + .keysize = 16, + .ivsize = 16, + .needs_essiv = true, + }, + [FSCRYPT_MODE_AES_128_CTS] = { + .friendly_name = "AES-128-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_ADIANTUM] = { + .friendly_name = "Adiantum", + .cipher_str = "adiantum(xchacha12,aes)", + .keysize = 32, + .ivsize = 32, + }, +}; + +static struct fscrypt_mode * +select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) +{ + if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { + fscrypt_warn(inode->i_sb, + "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", + inode->i_ino, ci->ci_data_mode, + ci->ci_filename_mode); + return ERR_PTR(-EINVAL); + } + + if (S_ISREG(inode->i_mode)) + return &available_modes[ci->ci_data_mode]; + + if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) + return &available_modes[ci->ci_filename_mode]; + + WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", + inode->i_ino, (inode->i_mode & S_IFMT)); + return ERR_PTR(-EINVAL); +} + +/* Create a symmetric cipher object for the given encryption mode and key */ +struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode, + const u8 *raw_key, + const struct inode *inode) +{ + struct crypto_skcipher *tfm; + int err; + + tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); + if (IS_ERR(tfm)) { + fscrypt_warn(inode->i_sb, + "error allocating '%s' transform for inode %lu: %ld", + mode->cipher_str, inode->i_ino, PTR_ERR(tfm)); + return tfm; + } + if (unlikely(!mode->logged_impl_name)) { + /* + * fscrypt performance can vary greatly depending on which + * crypto algorithm implementation is used. Help people debug + * performance problems by logging the ->cra_driver_name the + * first time a mode is used. Note that multiple threads can + * race here, but it doesn't really matter. + */ + mode->logged_impl_name = true; + pr_info("fscrypt: %s using implementation \"%s\"\n", + mode->friendly_name, + crypto_skcipher_alg(tfm)->base.cra_driver_name); + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); + if (err) + goto err_free_tfm; + + return tfm; + +err_free_tfm: + crypto_free_skcipher(tfm); + return ERR_PTR(err); +} + +static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) +{ + struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); + + /* init hash transform on demand */ + if (unlikely(!tfm)) { + struct crypto_shash *prev_tfm; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) { + fscrypt_warn(NULL, + "error allocating SHA-256 transform: %ld", + PTR_ERR(tfm)); + return PTR_ERR(tfm); + } + prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); + if (prev_tfm) { + crypto_free_shash(tfm); + tfm = prev_tfm; + } + } + + { + SHASH_DESC_ON_STACK(desc, tfm); + desc->tfm = tfm; + desc->flags = 0; + + return crypto_shash_digest(desc, key, keysize, salt); + } +} + +static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, + int keysize) +{ + int err; + struct crypto_cipher *essiv_tfm; + u8 salt[SHA256_DIGEST_SIZE]; + + if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE)) + return -EINVAL; + + essiv_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(essiv_tfm)) + return PTR_ERR(essiv_tfm); + + ci->ci_essiv_tfm = essiv_tfm; + + err = derive_essiv_salt(raw_key, keysize, salt); + if (err) + goto out; + + /* + * Using SHA256 to derive the salt/key will result in AES-256 being + * used for IV generation. File contents encryption will still use the + * configured keysize (AES-128) nevertheless. + */ + err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); + if (err) + goto out; + +out: + memzero_explicit(salt, sizeof(salt)); + return err; +} + +void __exit fscrypt_essiv_cleanup(void) +{ + crypto_free_shash(essiv_hash_tfm); +} + +/* Given the per-file key, set up the file's crypto transform object(s) */ +int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) +{ + struct fscrypt_mode *mode = ci->ci_mode; + struct crypto_skcipher *ctfm; + int err; + + ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode); + if (IS_ERR(ctfm)) + return PTR_ERR(ctfm); + + ci->ci_ctfm = ctfm; + + if (mode->needs_essiv) { + err = init_essiv_generator(ci, derived_key, mode->keysize); + if (err) { + fscrypt_warn(ci->ci_inode->i_sb, + "error initializing ESSIV generator for inode %lu: %d", + ci->ci_inode->i_ino, err); + return err; + } + } + return 0; +} + +/* + * Find the master key, then set up the inode's actual encryption key. + */ +static int setup_file_encryption_key(struct fscrypt_info *ci) +{ + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); +} + +static void put_crypt_info(struct fscrypt_info *ci) +{ + if (!ci) + return; + + if (ci->ci_direct_key) { + fscrypt_put_direct_key(ci->ci_direct_key); + } else { + crypto_free_skcipher(ci->ci_ctfm); + crypto_free_cipher(ci->ci_essiv_tfm); + } + kmem_cache_free(fscrypt_info_cachep, ci); +} + +int fscrypt_get_encryption_info(struct inode *inode) +{ + struct fscrypt_info *crypt_info; + struct fscrypt_context ctx; + struct fscrypt_mode *mode; + int res; + + if (inode->i_crypt_info) + return 0; + + res = fscrypt_initialize(inode->i_sb->s_cop->flags); + if (res) + return res; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res < 0) { + if (!fscrypt_dummy_context_enabled(inode) || + IS_ENCRYPTED(inode)) + return res; + /* Fake up a context for an unencrypted directory */ + memset(&ctx, 0, sizeof(ctx)); + ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; + ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.master_key_descriptor, 0x42, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + } else if (res != sizeof(ctx)) { + return -EINVAL; + } + + if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + return -EINVAL; + + if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) + return -EINVAL; + + crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); + if (!crypt_info) + return -ENOMEM; + + crypt_info->ci_inode = inode; + + crypt_info->ci_flags = ctx.flags; + crypt_info->ci_data_mode = ctx.contents_encryption_mode; + crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; + memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + + mode = select_encryption_mode(crypt_info, inode); + if (IS_ERR(mode)) { + res = PTR_ERR(mode); + goto out; + } + WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); + crypt_info->ci_mode = mode; + + res = setup_file_encryption_key(crypt_info); + if (res) + goto out; + + if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) + crypt_info = NULL; +out: + if (res == -ENOKEY) + res = 0; + put_crypt_info(crypt_info); + return res; +} +EXPORT_SYMBOL(fscrypt_get_encryption_info); + +void fscrypt_put_encryption_info(struct inode *inode) +{ + put_crypt_info(inode->i_crypt_info); + inode->i_crypt_info = NULL; +} +EXPORT_SYMBOL(fscrypt_put_encryption_info); diff --git a/fs/crypto/keysetup_legacy.c b/fs/crypto/keysetup_legacy.c new file mode 100644 index 0000000000000..407daa0b64d82 --- /dev/null +++ b/fs/crypto/keysetup_legacy.c @@ -0,0 +1,338 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup for v1 encryption policies + * + * Copyright 2015, 2019 Google LLC + */ + +/* + * This file implements compatibility functions for the original encryption + * policy version ("v1"), including: + * + * - Deriving per-file keys using the AES-128-ECB based KDF + * (rather than the new method of using HKDF-SHA512) + * + * - Retrieving fscrypt master keys from process-subscribed keyrings + * (rather than the new method of using a filesystem-level keyring) + * + * - Handling policies with the DIRECT_KEY flag set using a master key table + * (rather than the new method of implementing DIRECT_KEY with per-mode keys + * managed alongside the master keys in the filesystem-level keyring) + */ + +#include +#include +#include +#include +#include + +#include "fscrypt_private.h" + +/* Table of keys referenced by DIRECT_KEY policies */ +static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */ +static DEFINE_SPINLOCK(fscrypt_direct_keys_lock); + +/* + * Legacy key derivation function. This generates the derived key by encrypting + * the master key with AES-128-ECB using the nonce as the AES key. This + * provides a unique derived key with sufficient entropy for each inode. + * However, it's nonstandard, non-extensible, doesn't evenly distribute the + * entropy from the master key, and is trivially reversible: an attacker who + * compromises a derived key can "decrypt" it to get back to the master key, + * then derive any other key. For all new code, use HKDF instead. + * + * The master key must be at least as long as the derived key. If the master + * key is longer, then only the first 'derived_keysize' bytes are used. + */ +static int derive_key_aes(const u8 *master_key, + const u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE], + u8 *derived_key, unsigned int derived_keysize) +{ + int res = 0; + struct skcipher_request *req = NULL; + DECLARE_CRYPTO_WAIT(wait); + struct scatterlist src_sg, dst_sg; + struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); + + if (IS_ERR(tfm)) { + res = PTR_ERR(tfm); + tfm = NULL; + goto out; + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + req = skcipher_request_alloc(tfm, GFP_NOFS); + if (!req) { + res = -ENOMEM; + goto out; + } + skcipher_request_set_callback(req, + CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, + crypto_req_done, &wait); + res = crypto_skcipher_setkey(tfm, nonce, FS_KEY_DERIVATION_NONCE_SIZE); + if (res < 0) + goto out; + + sg_init_one(&src_sg, master_key, derived_keysize); + sg_init_one(&dst_sg, derived_key, derived_keysize); + skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, + NULL); + res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); +out: + skcipher_request_free(req); + crypto_free_skcipher(tfm); + return res; +} + +/* + * Search the current task's subscribed keyrings for a "logon" key with + * description prefix:descriptor, and if found acquire a read lock on it and + * return a pointer to its validated payload in *payload_ret. + */ +static struct key * +find_and_lock_process_key(const char *prefix, + const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], + unsigned int min_keysize, + const struct fscrypt_key **payload_ret) +{ + char *description; + struct key *key; + const struct user_key_payload *ukp; + const struct fscrypt_key *payload; + + description = kasprintf(GFP_NOFS, "%s%*phN", prefix, + FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); + if (!description) + return ERR_PTR(-ENOMEM); + + key = request_key(&key_type_logon, description, NULL); + kfree(description); + if (IS_ERR(key)) + return key; + + down_read(&key->sem); + ukp = user_key_payload_locked(key); + + if (!ukp) /* was the key revoked before we acquired its semaphore? */ + goto invalid; + + payload = (const struct fscrypt_key *)ukp->data; + + if (ukp->datalen != sizeof(struct fscrypt_key) || + payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { + fscrypt_warn(NULL, + "key with description '%s' has invalid payload", + key->description); + goto invalid; + } + + if (payload->size < min_keysize) { + fscrypt_warn(NULL, + "key with description '%s' is too short (got %u bytes, need %u+ bytes)", + key->description, payload->size, min_keysize); + goto invalid; + } + + *payload_ret = payload; + return key; + +invalid: + up_read(&key->sem); + key_put(key); + return ERR_PTR(-ENOKEY); +} + +/* Master key referenced by DIRECT_KEY policy */ +struct fscrypt_direct_key { + struct hlist_node dk_node; + refcount_t dk_refcount; + const struct fscrypt_mode *dk_mode; + struct crypto_skcipher *dk_ctfm; + u8 dk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + u8 dk_raw[FSCRYPT_MAX_KEY_SIZE]; +}; + +static void free_direct_key(struct fscrypt_direct_key *dk) +{ + if (dk) { + crypto_free_skcipher(dk->dk_ctfm); + kzfree(dk); + } +} + +void fscrypt_put_direct_key(struct fscrypt_direct_key *dk) +{ + if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock)) + return; + hash_del(&dk->dk_node); + spin_unlock(&fscrypt_direct_keys_lock); + + free_direct_key(dk); +} + +/* + * Find/insert the given key into the fscrypt_direct_keys table. If found, it + * is returned with elevated refcount, and 'to_insert' is freed if non-NULL. If + * not found, 'to_insert' is inserted and returned if it's non-NULL; otherwise + * NULL is returned. + */ +static struct fscrypt_direct_key * +find_or_insert_direct_key(struct fscrypt_direct_key *to_insert, + const u8 *raw_key, const struct fscrypt_info *ci) +{ + unsigned long hash_key; + struct fscrypt_direct_key *dk; + + /* + * Careful: to avoid potentially leaking secret key bytes via timing + * information, we must key the hash table by descriptor rather than by + * raw key, and use crypto_memneq() when comparing raw keys. + */ + + BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); + + spin_lock(&fscrypt_direct_keys_lock); + hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) { + if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) + continue; + if (ci->ci_mode != dk->dk_mode) + continue; + if (crypto_memneq(raw_key, dk->dk_raw, ci->ci_mode->keysize)) + continue; + /* using existing tfm with same (descriptor, mode, raw_key) */ + refcount_inc(&dk->dk_refcount); + spin_unlock(&fscrypt_direct_keys_lock); + free_direct_key(to_insert); + return dk; + } + if (to_insert) + hash_add(fscrypt_direct_keys, &to_insert->dk_node, hash_key); + spin_unlock(&fscrypt_direct_keys_lock); + return to_insert; +} + +/* Prepare to encrypt directly using the master key in the given mode */ +static struct fscrypt_direct_key * +fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key) +{ + struct fscrypt_direct_key *dk; + int err; + + /* Is there already a tfm for this key? */ + dk = find_or_insert_direct_key(NULL, raw_key, ci); + if (dk) + return dk; + + /* Nope, allocate one. */ + dk = kzalloc(sizeof(*dk), GFP_NOFS); + if (!dk) + return ERR_PTR(-ENOMEM); + refcount_set(&dk->dk_refcount, 1); + dk->dk_mode = ci->ci_mode; + dk->dk_ctfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, + ci->ci_inode); + if (IS_ERR(dk->dk_ctfm)) { + err = PTR_ERR(dk->dk_ctfm); + dk->dk_ctfm = NULL; + goto err_free_dk; + } + memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize); + + return find_or_insert_direct_key(dk, raw_key, ci); + +err_free_dk: + free_direct_key(dk); + return ERR_PTR(err); +} + +/* v1 policy, DIRECT_KEY: use the master key directly */ +static int setup_v1_file_key_direct(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + const struct fscrypt_mode *mode = ci->ci_mode; + struct fscrypt_direct_key *dk; + + if (!fscrypt_mode_supports_direct_key(mode)) { + fscrypt_warn(ci->ci_inode->i_sb, + "direct key flag not allowed with %s", + mode->friendly_name); + return -EINVAL; + } + + if (ci->ci_data_mode != ci->ci_filename_mode) { + fscrypt_warn(ci->ci_inode->i_sb, + "direct key flag not allowed with different contents and filenames modes"); + return -EINVAL; + } + + /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ + if (WARN_ON(mode->needs_essiv)) + return -EINVAL; + + dk = fscrypt_get_direct_key(ci, raw_master_key); + if (IS_ERR(dk)) + return PTR_ERR(dk); + ci->ci_direct_key = dk; + ci->ci_ctfm = dk->dk_ctfm; + return 0; +} + +/* v1 policy, !DIRECT_KEY: derive the file's encryption key */ +static int setup_v1_file_key_derived(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + u8 *derived_key; + int err; + + /* + * This cannot be a stack buffer because it will be passed to the + * scatterlist crypto API during derive_key_aes(). + */ + derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS); + if (!derived_key) + return -ENOMEM; + + err = derive_key_aes(raw_master_key, ci->ci_nonce, + derived_key, ci->ci_mode->keysize); + if (err) + goto out; + + err = fscrypt_set_derived_key(ci, derived_key); +out: + kzfree(derived_key); + return err; +} + +int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key) +{ + if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + return setup_v1_file_key_direct(ci, raw_master_key); + else + return setup_v1_file_key_derived(ci, raw_master_key); +} + +int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci) +{ + struct key *key; + const struct fscrypt_key *payload; + int err; + + key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, + ci->ci_master_key_descriptor, + ci->ci_mode->keysize, &payload); + if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) { + key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix, + ci->ci_master_key_descriptor, + ci->ci_mode->keysize, &payload); + } + if (IS_ERR(key)) + return PTR_ERR(key); + + err = fscrypt_setup_v1_file_key(ci, payload->raw); + up_read(&key->sem); + key_put(key); + return err; +} diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 8b1e444214973..5afb9fc13ef49 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -112,7 +112,7 @@ extern int fscrypt_ioctl_get_policy(struct file *, void __user *); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool); -/* keyinfo.c */ +/* keysetup.c */ extern int fscrypt_get_encryption_info(struct inode *); extern void fscrypt_put_encryption_info(struct inode *); @@ -312,7 +312,7 @@ static inline int fscrypt_inherit_context(struct inode *parent, return -EOPNOTSUPP; } -/* keyinfo.c */ +/* keysetup.c */ static inline int fscrypt_get_encryption_info(struct inode *inode) { return -EOPNOTSUPP; From patchwork Tue Apr 2 15:45:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10882003 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CE58015AC for ; Tue, 2 Apr 2019 15:49:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B4E4227F90 for ; Tue, 2 Apr 2019 15:49:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A8C09286A1; Tue, 2 Apr 2019 15:49:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4337A27F90 for ; Tue, 2 Apr 2019 15:49:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731647AbfDBPtW (ORCPT ); Tue, 2 Apr 2019 11:49:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:37006 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729722AbfDBPsg (ORCPT ); Tue, 2 Apr 2019 11:48:36 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9215C20882; Tue, 2 Apr 2019 15:48:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220113; bh=6bD6Iaa5+AAyrD3vbwL4Il9Ze0FuivYX6a/k2fiJu4c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JLsstx1bwePy3y41ghXAaTP29Gc1mIDK8vQbfG1vNpIeSeDka9CrsDw2oH85yPT/5 LwnypUYbWLvH7As6d20T8f99QYl8DjnHebQJtb8fKoyKHSQ4ufcINQ/QUhB5etvJax O35pJVGSVa7ZfL89Gd86GLgGVCGRRbSfejwnc7Tk= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 06/17] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Date: Tue, 2 Apr 2019 08:45:49 -0700 Message-Id: <20190402154600.32432-7-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY. This ioctl adds an encryption key to the filesystem's fscrypt keyring ->s_master_keys, making any files encrypted with that key appear "unlocked". Why we need this ~~~~~~~~~~~~~~~~ The main problem is that the "locked/unlocked" (ciphertext/plaintext) status of encrypted files is global, but the fscrypt keys are not. fscrypt only looks for keys in the keyring(s) the process accessing the filesystem is subscribed to: the thread keyring, process keyring, and session keyring, where the session keyring may contain the user keyring. Therefore, userspace has to put fscrypt keys in the keyrings for individual users or sessions. But this means that when a process with a different keyring tries to access encrypted files, whether they appear "unlocked" or not is nondeterministic. This is because it depends on whether the files are currently present in the inode cache. Fixing this by consistently providing each process its own view of the filesystem depending on whether it has the key or not isn't feasible due to how the VFS caches work. Furthermore, while sometimes users expect this behavior, it is misguided for two reasons. First, it would be an OS-level access control mechanism largely redundant with existing access control mechanisms such as UNIX file permissions, ACLs, LSMs, etc. Encryption is actually for protecting the data at rest. Second, almost all users of fscrypt actually do need the keys to be global. The largest users of fscrypt, Android and Chromium OS, achieve this by having PID 1 create a "session keyring" that is inherited by every process. This works, but it isn't scalable because it prevents session keyrings from being used for any other purpose. On general-purpose Linux distros, the 'fscrypt' userspace tool [1] can't similarly abuse the session keyring, so to make 'sudo' work on all systems it has to link all the user keyrings into root's user keyring [2]. This is ugly and raises security concerns. Moreover it can't make the keys available to system services, such as sshd trying to access the user's '~/.ssh' directory (see [3], [4]) or NetworkManager trying to read certificates from the user's home directory (see [5]). By having an API to add a key to the *filesystem* we'll be able to fix the above bugs, remove userspace workarounds, and clearly express the intended semantics: the locked/unlocked status of an encrypted directory is global, and encryption is orthogonal to OS-level access control. Why not use the add_key() syscall ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We use an ioctl for this API rather than the existing add_key() system call because the ioctl gives us the flexibility needed to implement fscrypt-specific semantics that will be introduced in later patches: - Supporting key removal with the semantics such that the secret is removed immediately and any unused inodes using the key are evicted; also, the eviction of any in-use inodes can be retried. - Calculating a key-dependent cryptographic identifier and returning it to userspace. - Allowing keys to be added and removed by non-root users, but only keys for v2 encryption policies; and to prevent denial-of-service attacks, users can only remove keys they themselves have added, and a key is only really removed after all users who added it have removed it. Trying to shoehorn these semantics into the keyrings syscalls would be very difficult, whereas the ioctls make things much easier. However, to reuse code the implementation still uses the keyrings service internally. Thus we get lockless RCU-mode key lookups without having to re-implement it, and the keys automatically show up in /proc/keys for debugging purposes. References: [1] https://github.com/google/fscrypt [2] https://goo.gl/55cCrI#heading=h.vf09isp98isb [3] https://github.com/google/fscrypt/issues/111#issuecomment-444347939 [4] https://github.com/google/fscrypt/issues/116 [5] https://bugs.launchpad.net/ubuntu/+source/fscrypt/+bug/1770715 Signed-off-by: Eric Biggers --- fs/crypto/Makefile | 1 + fs/crypto/crypto.c | 11 +- fs/crypto/fscrypt_private.h | 44 +++++- fs/crypto/keyring.c | 294 +++++++++++++++++++++++++++++++++++ fs/crypto/keysetup.c | 34 +++- fs/super.c | 2 + include/linux/fs.h | 1 + include/linux/fscrypt.h | 15 ++ include/uapi/linux/fscrypt.h | 40 +++-- 9 files changed, 429 insertions(+), 13 deletions(-) create mode 100644 fs/crypto/keyring.c diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile index 75c0c29fcc627..accdd622c9083 100644 --- a/fs/crypto/Makefile +++ b/fs/crypto/Makefile @@ -3,6 +3,7 @@ obj-$(CONFIG_FS_ENCRYPTION) += fscrypto.o fscrypto-y := crypto.o \ fname.o \ hooks.o \ + keyring.o \ keysetup.o \ keysetup_legacy.o \ policy.o diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 8217a44346215..8726c4e940773 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -451,6 +451,8 @@ void fscrypt_msg(struct super_block *sb, const char *level, */ static int __init fscrypt_init(void) { + int err = -ENOMEM; + /* * Use an unbound workqueue to allow bios to be decrypted in parallel * even when they happen to complete on the same CPU. This sacrifices @@ -473,14 +475,20 @@ static int __init fscrypt_init(void) if (!fscrypt_info_cachep) goto fail_free_ctx; + err = fscrypt_init_keyring(); + if (err) + goto fail_free_info; + return 0; +fail_free_info: + kmem_cache_destroy(fscrypt_info_cachep); fail_free_ctx: kmem_cache_destroy(fscrypt_ctx_cachep); fail_free_queue: destroy_workqueue(fscrypt_read_workqueue); fail: - return -ENOMEM; + return err; } module_init(fscrypt_init) @@ -497,6 +505,7 @@ static void __exit fscrypt_exit(void) kmem_cache_destroy(fscrypt_info_cachep); fscrypt_essiv_cleanup(); + fscrypt_exit_keyring(); } module_exit(fscrypt_exit); diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index c5a8181fc26c1..b4c4312085554 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -14,9 +14,12 @@ #include #include -/* Encryption parameters */ +#define CONST_STRLEN(str) (sizeof(str) - 1) + #define FS_KEY_DERIVATION_NONCE_SIZE 16 +#define FSCRYPT_MIN_KEY_SIZE 16 + /** * Encryption context for inode * @@ -159,6 +162,45 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); +/* keyring.c */ + +/* + * fscrypt_master_key_secret - secret key material of an in-use master key + */ +struct fscrypt_master_key_secret { + + /* Size of the raw key in bytes */ + u32 size; + + /* The raw key */ + u8 raw[FSCRYPT_MAX_KEY_SIZE]; + +} __randomize_layout; + +/* + * fscrypt_master_key - an in-use master key + * + * This represents a master encryption key which has been added to the + * filesystem and can be used to "unlock" the encrypted files which were + * encrypted with it. + */ +struct fscrypt_master_key { + + /* The secret key material */ + struct fscrypt_master_key_secret mk_secret; + + /* Arbitrary key descriptor which was assigned by userspace */ + struct fscrypt_key_specifier mk_spec; + +} __randomize_layout; + +extern struct key * +fscrypt_find_master_key(struct super_block *sb, + const struct fscrypt_key_specifier *mk_spec); + +extern int __init fscrypt_init_keyring(void); +extern void fscrypt_exit_keyring(void); + /* keysetup.c */ struct fscrypt_mode { diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c new file mode 100644 index 0000000000000..011aeb58806f7 --- /dev/null +++ b/fs/crypto/keyring.c @@ -0,0 +1,294 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Filesystem-level keyring for fscrypt + * + * Copyright 2019 Google LLC + */ + +/* + * This file implements management of fscrypt master keys in the + * filesystem-level keyring, including the ioctls: + * + * - FS_IOC_ADD_ENCRYPTION_KEY: add a key + */ + +#include +#include + +#include "fscrypt_private.h" + +static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret) +{ + memzero_explicit(secret, sizeof(*secret)); +} + +static void move_master_key_secret(struct fscrypt_master_key_secret *dst, + struct fscrypt_master_key_secret *src) +{ + memcpy(dst, src, sizeof(*dst)); + memzero_explicit(src, sizeof(*src)); +} + +static void free_master_key(struct fscrypt_master_key *mk) +{ + wipe_master_key_secret(&mk->mk_secret); + kzfree(mk); +} + +static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec) +{ + switch (spec->type) { + case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: + return FSCRYPT_KEY_DESCRIPTOR_SIZE; + } + return 0; +} + +static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec) +{ + if (spec->__reserved) + return false; + return master_key_spec_len(spec) != 0; +} + +static int fscrypt_key_instantiate(struct key *key, + struct key_preparsed_payload *prep) +{ + key->payload.data[0] = (struct fscrypt_master_key *)prep->data; + return 0; +} + +static void fscrypt_key_destroy(struct key *key) +{ + free_master_key(key->payload.data[0]); +} + +static void fscrypt_key_describe(const struct key *key, struct seq_file *m) +{ + seq_puts(m, key->description); +} + +/* + * Type of key in ->s_master_keys. Each key of this type represents a master + * key which has been added to the filesystem. Its payload is a + * 'struct fscrypt_master_key'. The "." prefix in the key type name prevents + * users from adding keys of this type via the keyrings syscalls rather than via + * the intended method of FS_IOC_ADD_ENCRYPTION_KEY. + */ +static struct key_type key_type_fscrypt = { + .name = "._fscrypt", + .instantiate = fscrypt_key_instantiate, + .destroy = fscrypt_key_destroy, + .describe = fscrypt_key_describe, +}; + +/* Search ->s_master_keys */ +static struct key *search_fscrypt_keyring(struct key *keyring, + struct key_type *type, + const char *description) +{ + /* + * We need to mark the keyring reference as "possessed" so that we + * acquire permission to search it, via the KEY_POS_SEARCH permission. + */ + key_ref_t keyref = make_key_ref(keyring, true); + + keyref = keyring_search(keyref, type, description); + if (IS_ERR(keyref)) { + if (PTR_ERR(keyref) == -EAGAIN || /* not found */ + PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */ + keyref = ERR_PTR(-ENOKEY); + return ERR_CAST(keyref); + } + return key_ref_to_ptr(keyref); +} + +#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ + (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id)) + +#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1) + +static void format_fs_keyring_description( + char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], + const struct super_block *sb) +{ + sprintf(description, "fscrypt-%s", sb->s_id); +} + +static void format_mk_description( + char description[FSCRYPT_MK_DESCRIPTION_SIZE], + const struct fscrypt_key_specifier *mk_spec) +{ + sprintf(description, "%*phN", + master_key_spec_len(mk_spec), (u8 *)&mk_spec->u); +} + +/* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ +static int allocate_filesystem_keyring(struct super_block *sb) +{ + char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE]; + struct key *keyring; + + if (sb->s_master_keys) + return 0; + + format_fs_keyring_description(description, sb); + keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, + current_cred(), KEY_POS_SEARCH | + KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); + + /* Pairs with smp_load_acquire() in fscrypt_find_master_key() */ + smp_store_release(&sb->s_master_keys, keyring); + return 0; +} + +void fscrypt_sb_free(struct super_block *sb) +{ + key_put(sb->s_master_keys); + sb->s_master_keys = NULL; +} + +/* + * Find the specified master key in ->s_master_keys. + * Returns ERR_PTR(-ENOKEY) if not found. + */ +struct key *fscrypt_find_master_key(struct super_block *sb, + const struct fscrypt_key_specifier *mk_spec) +{ + struct key *keyring; + char description[FSCRYPT_MK_DESCRIPTION_SIZE]; + + /* pairs with smp_store_release() in allocate_filesystem_keyring() */ + keyring = smp_load_acquire(&sb->s_master_keys); + if (keyring == NULL) + return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */ + + format_mk_description(description, mk_spec); + return search_fscrypt_keyring(keyring, &key_type_fscrypt, description); +} + +/* + * Allocate a new fscrypt_master_key which contains the given secret, set it as + * the payload of a new 'struct key' of type fscrypt, and link the 'struct key' + * into the given keyring. Synchronized by fscrypt_add_key_mutex. + */ +static int add_new_master_key(struct fscrypt_master_key_secret *secret, + const struct fscrypt_key_specifier *mk_spec, + struct key *keyring) +{ + struct fscrypt_master_key *mk; + char description[FSCRYPT_MK_DESCRIPTION_SIZE]; + struct key *key; + int err; + + mk = kzalloc(sizeof(*mk), GFP_NOFS); + if (!mk) + return -ENOMEM; + + mk->mk_spec = *mk_spec; + + move_master_key_secret(&mk->mk_secret, secret); + + format_mk_description(description, mk_spec); + key = key_alloc(&key_type_fscrypt, description, + GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), + KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL); + if (IS_ERR(key)) { + err = PTR_ERR(key); + goto out_free_mk; + } + err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL); + key_put(key); + if (err) + goto out_free_mk; + + return 0; + +out_free_mk: + free_master_key(mk); + return err; +} + +static int add_master_key(struct super_block *sb, + struct fscrypt_master_key_secret *secret, + const struct fscrypt_key_specifier *mk_spec) +{ + static DEFINE_MUTEX(fscrypt_add_key_mutex); + struct key *key; + int err; + + mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */ + key = fscrypt_find_master_key(sb, mk_spec); + if (IS_ERR(key)) { + err = PTR_ERR(key); + if (err != -ENOKEY) + goto out_unlock; + /* Didn't find the key in ->s_master_keys. Add it. */ + err = allocate_filesystem_keyring(sb); + if (err) + goto out_unlock; + err = add_new_master_key(secret, mk_spec, sb->s_master_keys); + } else { + key_put(key); + err = 0; + } +out_unlock: + mutex_unlock(&fscrypt_add_key_mutex); + return err; +} + +/* + * Add a master encryption key to the filesystem, causing all files which were + * encrypted with it to appear "unlocked" (decrypted) when accessed. + */ +int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_add_key_arg __user *uarg = _uarg; + struct fscrypt_add_key_arg arg; + struct fscrypt_master_key_secret secret; + int err; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE || + arg.raw_size > FSCRYPT_MAX_KEY_SIZE) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + memset(&secret, 0, sizeof(secret)); + secret.size = arg.raw_size; + err = -EFAULT; + if (copy_from_user(secret.raw, uarg->raw, secret.size)) + goto out_wipe_secret; + + err = -EACCES; + if (!capable(CAP_SYS_ADMIN)) + goto out_wipe_secret; + + err = add_master_key(sb, &secret, &arg.key_spec); +out_wipe_secret: + wipe_master_key_secret(&secret); + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key); + +int __init fscrypt_init_keyring(void) +{ + return register_key_type(&key_type_fscrypt); +} + +void fscrypt_exit_keyring(void) +{ + unregister_key_type(&key_type_fscrypt); +} diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index 829b74974e8f6..f3a476df97c64 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -213,7 +213,39 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) */ static int setup_file_encryption_key(struct fscrypt_info *ci) { - return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); + struct key *key; + struct fscrypt_master_key *mk = NULL; + struct fscrypt_key_specifier mk_spec; + int err; + + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; + memcpy(mk_spec.u.descriptor, ci->ci_master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + + key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec); + if (IS_ERR(key)) { + if (key != ERR_PTR(-ENOKEY)) + return PTR_ERR(key); + + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); + } + + mk = key->payload.data[0]; + + if (mk->mk_secret.size < ci->ci_mode->keysize) { + fscrypt_warn(NULL, + "key with description '%s' is too short (got %u bytes, need %u+ bytes)", + key->description, mk->mk_secret.size, + ci->ci_mode->keysize); + err = -ENOKEY; + goto out_release_key; + } + + err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + +out_release_key: + key_put(key); + return err; } static void put_crypt_info(struct fscrypt_info *ci) diff --git a/fs/super.c b/fs/super.c index 583a0124bc394..ae3661ade8f32 100644 --- a/fs/super.c +++ b/fs/super.c @@ -32,6 +32,7 @@ #include #include #include +#include #include #include #include @@ -290,6 +291,7 @@ static void __put_super(struct super_block *s) WARN_ON(s->s_inode_lru.node); WARN_ON(!list_empty(&s->s_mounts)); security_sb_free(s); + fscrypt_sb_free(s); put_user_ns(s->s_user_ns); kfree(s->s_subtype); call_rcu(&s->rcu, destroy_super_rcu); diff --git a/include/linux/fs.h b/include/linux/fs.h index 8b42df09b04c9..17c6a74860e1c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1420,6 +1420,7 @@ struct super_block { const struct xattr_handler **s_xattr; #ifdef CONFIG_FS_ENCRYPTION const struct fscrypt_operations *s_cop; + struct key *s_master_keys; /* master crypto keys in use */ #endif struct hlist_bl_head s_roots; /* alternate root dentries for NFS */ struct list_head s_mounts; /* list of mounts; _not_ for fs use */ diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 5afb9fc13ef49..e43c61fcb1125 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -112,6 +112,10 @@ extern int fscrypt_ioctl_get_policy(struct file *, void __user *); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool); +/* keyring.c */ +extern void fscrypt_sb_free(struct super_block *sb); +extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg); + /* keysetup.c */ extern int fscrypt_get_encryption_info(struct inode *); extern void fscrypt_put_encryption_info(struct inode *); @@ -312,6 +316,17 @@ static inline int fscrypt_inherit_context(struct inode *parent, return -EOPNOTSUPP; } +/* keyring.c */ +static inline void fscrypt_sb_free(struct super_block *sb) +{ + return; +} + +static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + /* keysetup.c */ static inline int fscrypt_get_encryption_info(struct inode *inode) { diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 3bbc5dfbde211..7bed24632bda7 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -34,22 +34,42 @@ struct fscrypt_policy { __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; }; -#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) -#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) -#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) - -/* Parameters for passing an encryption key into the kernel keyring */ +/* + * Process-subscribed "logon" key description prefix and payload format. + * Deprecated; prefer FS_IOC_ADD_ENCRYPTION_KEY instead. + */ #define FSCRYPT_KEY_DESC_PREFIX "fscrypt:" -#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8 - -/* Structure that userspace passes to the kernel keyring */ -#define FSCRYPT_MAX_KEY_SIZE 64 - +#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8 +#define FSCRYPT_MAX_KEY_SIZE 64 struct fscrypt_key { __u32 mode; __u8 raw[FSCRYPT_MAX_KEY_SIZE]; __u32 size; }; + +struct fscrypt_key_specifier { +#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR 1 + __u32 type; + __u32 __reserved; + union { + __u8 __reserved[32]; /* reserve some extra space */ + __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + } u; +}; + +/* Struct passed to FS_IOC_ADD_ENCRYPTION_KEY */ +struct fscrypt_add_key_arg { + struct fscrypt_key_specifier key_spec; + __u32 raw_size; + __u32 __reserved[9]; + __u8 raw[]; +}; + +#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) +#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) +#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) +#define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg) + /**********************************************************************/ /* old names; don't add anything new here! */ From patchwork Tue Apr 2 15:45:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881921 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 792A0184E for ; Tue, 2 Apr 2019 15:48:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 69C96201F5 for ; Tue, 2 Apr 2019 15:48:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5DE07287CC; Tue, 2 Apr 2019 15:48:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0DFED2868C for ; Tue, 2 Apr 2019 15:48:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731394AbfDBPsj (ORCPT ); Tue, 2 Apr 2019 11:48:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:37018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730664AbfDBPsf (ORCPT ); Tue, 2 Apr 2019 11:48:35 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0E9602146E; Tue, 2 Apr 2019 15:48:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220114; bh=ZS9y98i16xygu0zu+wJ3ifdcMp238qH7OAyxgKi2mvw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DZBFMH0vSgg9muf0p7CxAXRE4+kBgTnryrfHGeqtHuyMQh6MkW5Rnk64wUKv4Gka8 dX1SPoqS5MSqc7ovL2tIRqD7DFoeDf4f6+uud/PTvi8vNAjPHp6rvGT3sSEWBKPYA2 DTbsulOBb1PAKa43ipPUdYtoGqDeXl0x68gopxPo= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 07/17] fs/dcache.c: add shrink_dcache_inode() Date: Tue, 2 Apr 2019 08:45:50 -0700 Message-Id: <20190402154600.32432-8-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers When a filesystem encryption key is removed, we need all files which had been "unlocked" (had ->i_crypt_info set up) with it to appear "locked" again. This is most easily done by evicting the inodes. This can currently be done using 'echo 2 > /proc/sys/vm/drop_caches'; however, that is overkill and not usable by non-root users. To evict just the needed inodes we also need the ability to evict those inodes' dentries, since an inode is pinned by its dentries. Therefore, add a function shrink_dcache_inode() which iterates through an inode's dentries and evicts any unused ones as well as any unused descendants (since there may be negative dentries pinning the inode's dentries). Signed-off-by: Eric Biggers --- fs/dcache.c | 32 ++++++++++++++++++++++++++++++++ include/linux/dcache.h | 1 + 2 files changed, 33 insertions(+) diff --git a/fs/dcache.c b/fs/dcache.c index aac41adf47433..1d940484c2d17 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1507,6 +1507,38 @@ void shrink_dcache_parent(struct dentry *parent) } EXPORT_SYMBOL(shrink_dcache_parent); +/** + * shrink_dcache_inode - prune dcache for inode + * @inode: inode to prune + * + * Evict all unused aliases of the specified inode from the dcache. This is + * intended to be used when trying to evict a specific inode, since inodes are + * pinned by their dentries. We also have to descend to ->d_subdirs for each + * alias, since aliases may be pinned by negative child dentries. + */ +void shrink_dcache_inode(struct inode *inode) +{ + for (;;) { + struct select_data data; + struct dentry *dentry; + + INIT_LIST_HEAD(&data.dispose); + data.start = NULL; + data.found = 0; + + spin_lock(&inode->i_lock); + hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) + d_walk(dentry, &data, select_collect); + spin_unlock(&inode->i_lock); + + if (!data.found) + break; + + shrink_dentry_list(&data.dispose); + cond_resched(); + } +} + static enum d_walk_ret umount_check(void *_data, struct dentry *dentry) { /* it has busy descendents; complain about those instead */ diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 60996e64c5798..1b5f295dc1156 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -246,6 +246,7 @@ extern struct dentry * d_obtain_alias(struct inode *); extern struct dentry * d_obtain_root(struct inode *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); +extern void shrink_dcache_inode(struct inode *); extern void shrink_dcache_for_umount(struct super_block *); extern void d_invalidate(struct dentry *); From patchwork Tue Apr 2 15:45:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881993 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6D6281800 for ; Tue, 2 Apr 2019 15:49:20 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 559CA2868C for ; Tue, 2 Apr 2019 15:49:20 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4A021287C8; Tue, 2 Apr 2019 15:49:20 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E59E8286A1 for ; Tue, 2 Apr 2019 15:49:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731623AbfDBPtO (ORCPT ); Tue, 2 Apr 2019 11:49:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:37032 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731210AbfDBPsg (ORCPT ); Tue, 2 Apr 2019 11:48:36 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 812FE2148E; Tue, 2 Apr 2019 15:48:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220114; bh=Ilc+Pnqqi2QKhzSecabwPv8wUE+pWGg9zAGTM55kuTs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EBhDsG8w8AZd5V6g+oEHBjauSCftjHfJ/5bgiiwFoIq89LEK2uj+Fail59EeWvb2Q He8I5OyoSme5STrIaKAc+usswimGEVFltV5+Yuc2pemzHn38D/OXIsBVbB72UH8FsB dVuhEpdKVrBTvTr8TSjrQb5J2F+szBuAoKWAtGtY= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 08/17] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Date: Tue, 2 Apr 2019 08:45:51 -0700 Message-Id: <20190402154600.32432-9-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add a new fscrypt ioctl, FS_IOC_REMOVE_ENCRYPTION_KEY. This ioctl removes an encryption key that was added by FS_IOC_ADD_ENCRYPTION_KEY. It wipes the secret key itself, then "locks" the encrypted files and directories that had been unlocked using that key -- implemented by evicting the relevant dentries and inodes from the VFS caches. The problem this solves is that many fscrypt users want the ability to remove encryption keys, causing the corresponding encrypted directories to appear "locked" (presented in ciphertext form) again. Moreover, users want removing an encryption key to *really* remove it, in the sense that the removed keys cannot be recovered even if kernel memory is compromised, e.g. by the exploit of a kernel security vulnerability or by a physical attack. This is desirable after a user logs out of the system, for example. In many cases users even already assume this to be the case and are surprised to hear when it's not. It is not sufficient to simply unlink the master key from the keyring (or to revoke or invalidate it), since the actual encryption transform objects are still pinned in memory by their inodes. Therefore, to really remove a key we must also evict the relevant inodes. Currently one workaround is to run 'sync && echo 2 > /proc/sys/vm/drop_caches'. But, that evicts all unused inodes in the system rather than just the inodes associated with the key being removed, causing severe performance problems. Moreover, it requires root privileges, so regular users can't "lock" their encrypted files. Another workaround, used in Chromium OS kernels, is to add a new VFS-level ioctl FS_IOC_DROP_CACHE which is a more restricted version of drop_caches that operates on a single super_block. It does: shrink_dcache_sb(sb); invalidate_inodes(sb, false); But it's still a hack. Yet, the major users of filesystem encryption want this feature badly enough that they are actually using these hacks. To properly solve the problem, start maintaining a list of the inodes which have been "unlocked" using each master key. Originally this wasn't possible because the kernel didn't keep track of in-use master keys at all. But, with the ->s_master_keys keyring it is now possible. Then, add an ioctl FS_IOC_REMOVE_ENCRYPTION_KEY. It finds the specified master key in ->s_master_keys, then wipes the secret key itself, which prevents any additional inodes from being unlocked with the key. Then, it syncs the filesystem and evicts the inodes in the key's list. The normal inode eviction code will free and wipe the per-file keys (in ->i_crypt_info). Note that freeing ->i_crypt_info without evicting the inodes was also considered, but would have been racy. Some inodes may still be in use when a master key is removed, and we can't simply revoke random file descriptors, mmap's, etc. Thus, the ioctl simply skips in-use inodes, and returns -EBUSY to indicate that some inodes weren't evicted. The master key *secret* is still removed, but the fscrypt_master_key struct remains to keep track of the remaining inodes. Userspace can then retry the ioctl to evict the remaining inodes. Alternatively, if userspace adds the key again, the refreshed secret will be associated with the existing list of inodes so they remain correctly tracked for future key removals. The ioctl doesn't wipe pagecache pages. Thus, we tolerate that after a kernel compromise some portions of plaintext file contents may still be recoverable from memory. This can be solved be enabling page poisoning system-wide, which security conscious users may choose to do. But it's very difficult to solve otherwise, e.g. note that plaintext file contents may have been read in other places than pagecache pages. Like FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY is initially restricted to privileged users only. This is sufficient for some use cases, but not all. A later patch will relax this restriction, but it will require introducing key hashes, among other changes. Signed-off-by: Eric Biggers --- fs/crypto/fscrypt_private.h | 53 ++++++++- fs/crypto/keyring.c | 201 ++++++++++++++++++++++++++++++++++- fs/crypto/keysetup.c | 103 +++++++++++++++++- include/linux/fscrypt.h | 13 +++ include/uapi/linux/fscrypt.h | 7 ++ 5 files changed, 372 insertions(+), 5 deletions(-) diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index b4c4312085554..cc1862c9baa1d 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -78,6 +78,19 @@ struct fscrypt_info { /* Back-pointer to the inode */ struct inode *ci_inode; + /* + * The master key with which this inode was unlocked (decrypted). This + * will be NULL if the master key was found in a process-subscribed + * keyring rather than in the filesystem-level keyring. + */ + struct key *ci_master_key; + + /* + * Link in list of inodes that were unlocked with the master key. + * Only used when ->ci_master_key is set. + */ + struct list_head ci_master_key_link; + /* * If non-NULL, then encryption is done using the master key directly * and ci_ctfm will equal ci_direct_key->dk_ctfm. @@ -186,14 +199,52 @@ struct fscrypt_master_key_secret { */ struct fscrypt_master_key { - /* The secret key material */ + /* + * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is + * executed, this is wiped and no new inodes can be unlocked with this + * key; however, there may still be inodes in ->mk_decrypted_inodes + * which could not be evicted. As long as some inodes still remain, + * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or + * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again. + * + * Locking: protected by key->sem. + */ struct fscrypt_master_key_secret mk_secret; /* Arbitrary key descriptor which was assigned by userspace */ struct fscrypt_key_specifier mk_spec; + /* + * Length of ->mk_decrypted_inodes, plus one if mk_secret is present. + * Once this goes to 0, the master key is removed from ->s_master_keys. + * The 'struct fscrypt_master_key' will continue to live as long as the + * 'struct key' whose payload it is, but we won't let this reference + * count rise again. + */ + refcount_t mk_refcount; + + /* + * List of inodes that were unlocked using this key. This allows the + * inodes to be evicted efficiently if the key is removed. + */ + struct list_head mk_decrypted_inodes; + spinlock_t mk_decrypted_inodes_lock; + } __randomize_layout; +static inline bool +is_master_key_secret_present(const struct fscrypt_master_key_secret *secret) +{ + /* + * The READ_ONCE() is only necessary for fscrypt_drop_inode() and + * fscrypt_key_describe(). These run in atomic context, so they can't + * take key->sem and thus 'secret' can change concurrently which would + * be a data race. But they only need to know whether the secret *was* + * present at the time of check, so READ_ONCE() suffices. + */ + return READ_ONCE(secret->size) != 0; +} + extern struct key * fscrypt_find_master_key(struct super_block *sb, const struct fscrypt_key_specifier *mk_spec); diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 011aeb58806f7..ee9be002c1490 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -10,6 +10,7 @@ * filesystem-level keyring, including the ioctls: * * - FS_IOC_ADD_ENCRYPTION_KEY: add a key + * - FS_IOC_REMOVE_ENCRYPTION_KEY: remove a key */ #include @@ -66,6 +67,13 @@ static void fscrypt_key_destroy(struct key *key) static void fscrypt_key_describe(const struct key *key, struct seq_file *m) { seq_puts(m, key->description); + + if (key_is_positive(key)) { + const struct fscrypt_master_key *mk = key->payload.data[0]; + + if (!is_master_key_secret_present(&mk->mk_secret)) + seq_puts(m, ": secret removed"); + } } /* @@ -192,6 +200,10 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret, move_master_key_secret(&mk->mk_secret, secret); + refcount_set(&mk->mk_refcount, 1); /* secret is present */ + INIT_LIST_HEAD(&mk->mk_decrypted_inodes); + spin_lock_init(&mk->mk_decrypted_inodes_lock); + format_mk_description(description, mk_spec); key = key_alloc(&key_type_fscrypt, description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), @@ -213,6 +225,22 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret, return err; } +#define KEY_DEAD 1 + +static int add_existing_master_key(struct fscrypt_master_key *mk, + struct fscrypt_master_key_secret *secret, + const struct fscrypt_key_specifier *mk_spec) +{ + if (is_master_key_secret_present(&mk->mk_secret)) + return 0; + + if (!refcount_inc_not_zero(&mk->mk_refcount)) + return KEY_DEAD; + + move_master_key_secret(&mk->mk_secret, secret); + return 0; +} + static int add_master_key(struct super_block *sb, struct fscrypt_master_key_secret *secret, const struct fscrypt_key_specifier *mk_spec) @@ -222,6 +250,7 @@ static int add_master_key(struct super_block *sb, int err; mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */ +retry: key = fscrypt_find_master_key(sb, mk_spec); if (IS_ERR(key)) { err = PTR_ERR(key); @@ -233,8 +262,21 @@ static int add_master_key(struct super_block *sb, goto out_unlock; err = add_new_master_key(secret, mk_spec, sb->s_master_keys); } else { + /* + * Found the key in ->s_master_keys. Re-add the secret if + * needed. + */ + down_write(&key->sem); + err = add_existing_master_key(key->payload.data[0], secret, + mk_spec); + up_write(&key->sem); + if (err == KEY_DEAD) { + /* Key being removed or needs to be removed */ + key_invalidate(key); + key_put(key); + goto retry; + } key_put(key); - err = 0; } out_unlock: mutex_unlock(&fscrypt_add_key_mutex); @@ -283,6 +325,163 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) } EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key); +static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk) +{ + struct fscrypt_info *ci; + struct inode *inode; + struct inode *toput_inode = NULL; + + spin_lock(&mk->mk_decrypted_inodes_lock); + + list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) { + inode = ci->ci_inode; + spin_lock(&inode->i_lock); + if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) { + spin_unlock(&inode->i_lock); + continue; + } + __iget(inode); + spin_unlock(&inode->i_lock); + spin_unlock(&mk->mk_decrypted_inodes_lock); + + shrink_dcache_inode(inode); + iput(toput_inode); + toput_inode = inode; + + spin_lock(&mk->mk_decrypted_inodes_lock); + } + + spin_unlock(&mk->mk_decrypted_inodes_lock); + iput(toput_inode); +} + +static int try_to_lock_encrypted_files(struct super_block *sb, + struct fscrypt_master_key *mk) +{ + int err1; + int err2; + + /* + * An inode can't be evicted while it is dirty or has dirty pages. + * Thus, we first have to clean the inodes in ->mk_decrypted_inodes. + * + * Just do it the easy way: call sync_filesystem(). It's overkill, but + * it works, and it's more important to minimize the amount of caches we + * drop than the amount of data we sync. Also, unprivileged users can + * already call sync_filesystem() via sys_syncfs() or sys_sync(). + */ + down_read(&sb->s_umount); + err1 = sync_filesystem(sb); + up_read(&sb->s_umount); + /* If a sync error occurs, still try to evict as much as possible. */ + + /* + * Inodes are pinned by their dentries, so we have to evict their + * dentries. shrink_dcache_sb() would suffice, but would be overkill + * and inappropriate for use by unprivileged users. So instead go + * through the inodes' alias lists and try to evict each dentry. + */ + evict_dentries_for_decrypted_inodes(mk); + + /* + * evict_dentries_for_decrypted_inodes() already iput() each inode in + * the list; any inodes for which that dropped the last reference will + * have been evicted due to fscrypt_drop_inode() detecting the key + * removal and telling the VFS to evict the inode. So to finish, we + * just need to check whether any inodes couldn't be evicted. + */ + err2 = 0; + spin_lock(&mk->mk_decrypted_inodes_lock); + if (!list_empty(&mk->mk_decrypted_inodes)) { + const struct fscrypt_info *first_ci = + list_first_entry(&mk->mk_decrypted_inodes, + struct fscrypt_info, + ci_master_key_link); + fscrypt_warn(sb, + "inodes still busy after removing key with description %*phN (first ino: %lu)", + master_key_spec_len(&mk->mk_spec), + (u8 *)&mk->mk_spec.u, first_ci->ci_inode->i_ino); + err2 = -EBUSY; + } + spin_unlock(&mk->mk_decrypted_inodes_lock); + + return err1 ?: err2; +} + +/* + * Try to remove an fscrypt master encryption key. If other users have also + * added the key, we'll remove the current user's usage of the key, then return + * -EUSERS. Otherwise we'll continue on and try to actually remove the key. + * + * First we wipe the actual master key secret from memory, so that no more + * inodes can be unlocked with it. Then, we try to evict all cached inodes that + * had been unlocked using the key. Since this can fail for in-use inodes, this + * is expected to be used in cooperation with userspace ensuring that none of + * the files are still open. + * + * If, nevertheless, some inodes could not be evicted, we return -EBUSY + * (although we still evicted as many inodes as possible) and keep the 'struct + * key' and the 'struct fscrypt_master_key' around to keep track of the list of + * remaining inodes. Userspace can then retry the ioctl later to retry evicting + * the remaining inodes, or alternatively can add the secret key again. + * + * Note that even though we wipe the encryption *keys* from memory, decrypted + * data can likely still be found in memory, e.g. in pagecache pages that have + * been freed. Wiping such data is currently out of scope, short of users who + * may choose to enable page and slab poisoning systemwide. + */ +int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_remove_key_arg arg; + struct key *key; + struct fscrypt_master_key *mk; + int err; + bool dead; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EACCES; + + /* Find the key being removed. */ + key = fscrypt_find_master_key(sb, &arg.key_spec); + if (IS_ERR(key)) + return PTR_ERR(key); + mk = key->payload.data[0]; + + down_write(&key->sem); + + /* Wipe the secret. */ + dead = false; + if (is_master_key_secret_present(&mk->mk_secret)) { + wipe_master_key_secret(&mk->mk_secret); + dead = refcount_dec_and_test(&mk->mk_refcount); + } + up_write(&key->sem); + if (dead) { + /* + * We wiped the secret and no inodes reference the key anymore, + * so it's free to remove. + */ + key_invalidate(key); + err = 0; + } else { + /* Some inodes still reference this key; try to evict them. */ + err = try_to_lock_encrypted_files(sb, mk); + } + key_put(key); + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key); + int __init fscrypt_init_keyring(void) { return register_key_type(&key_type_fscrypt); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index f3a476df97c64..f8fb115c63ab9 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -210,8 +210,16 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) /* * Find the master key, then set up the inode's actual encryption key. + * + * If the master key is found in the filesystem-level keyring, then the + * corresponding 'struct key' is returned in *master_key_ret with + * ->sem read-locked. This is needed to ensure that only one task links the + * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create + * an fscrypt_info for the same inode), and to synchronize the key being removed + * with a new inode starting to use it. */ -static int setup_file_encryption_key(struct fscrypt_info *ci) +static int setup_file_encryption_key(struct fscrypt_info *ci, + struct key **master_key_ret) { struct key *key; struct fscrypt_master_key *mk = NULL; @@ -231,6 +239,13 @@ static int setup_file_encryption_key(struct fscrypt_info *ci) } mk = key->payload.data[0]; + down_read(&key->sem); + + /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ + if (!is_master_key_secret_present(&mk->mk_secret)) { + err = -ENOKEY; + goto out_release_key; + } if (mk->mk_secret.size < ci->ci_mode->keysize) { fscrypt_warn(NULL, @@ -242,14 +257,22 @@ static int setup_file_encryption_key(struct fscrypt_info *ci) } err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + if (err) + goto out_release_key; + + *master_key_ret = key; + return 0; out_release_key: + up_read(&key->sem); key_put(key); return err; } static void put_crypt_info(struct fscrypt_info *ci) { + struct key *key; + if (!ci) return; @@ -259,6 +282,26 @@ static void put_crypt_info(struct fscrypt_info *ci) crypto_free_skcipher(ci->ci_ctfm); crypto_free_cipher(ci->ci_essiv_tfm); } + + key = ci->ci_master_key; + if (key) { + struct fscrypt_master_key *mk = key->payload.data[0]; + + /* + * Remove this inode from the list of inodes that were unlocked + * with the master key. + * + * In addition, if we're removing the last inode from a key that + * already had its secret removed, invalidate the key so that it + * gets removed from ->s_master_keys. + */ + spin_lock(&mk->mk_decrypted_inodes_lock); + list_del(&ci->ci_master_key_link); + spin_unlock(&mk->mk_decrypted_inodes_lock); + if (refcount_dec_and_test(&mk->mk_refcount)) + key_invalidate(key); + key_put(key); + } kmem_cache_free(fscrypt_info_cachep, ci); } @@ -267,6 +310,7 @@ int fscrypt_get_encryption_info(struct inode *inode) struct fscrypt_info *crypt_info; struct fscrypt_context ctx; struct fscrypt_mode *mode; + struct key *master_key = NULL; int res; if (inode->i_crypt_info) @@ -319,13 +363,30 @@ int fscrypt_get_encryption_info(struct inode *inode) WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); crypt_info->ci_mode = mode; - res = setup_file_encryption_key(crypt_info); + res = setup_file_encryption_key(crypt_info, &master_key); if (res) goto out; - if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) + if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) { + if (master_key) { + struct fscrypt_master_key *mk = + master_key->payload.data[0]; + + refcount_inc(&mk->mk_refcount); + crypt_info->ci_master_key = key_get(master_key); + spin_lock(&mk->mk_decrypted_inodes_lock); + list_add(&crypt_info->ci_master_key_link, + &mk->mk_decrypted_inodes); + spin_unlock(&mk->mk_decrypted_inodes_lock); + } crypt_info = NULL; + } + res = 0; out: + if (master_key) { + up_read(&master_key->sem); + key_put(master_key); + } if (res == -ENOKEY) res = 0; put_crypt_info(crypt_info); @@ -339,3 +400,39 @@ void fscrypt_put_encryption_info(struct inode *inode) inode->i_crypt_info = NULL; } EXPORT_SYMBOL(fscrypt_put_encryption_info); + +/** + * fscrypt_drop_inode() - check whether the inode's master key has been removed + * + * Filesystems supporting fscrypt must call this from their ->drop_inode() + * method so that encrypted inodes are evicted as soon as they're no longer in + * use and their master key has been removed. + * + * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 + */ +int fscrypt_drop_inode(struct inode *inode) +{ + const struct fscrypt_info *ci = inode->i_crypt_info; + const struct fscrypt_master_key *mk; + + /* + * If ci is NULL, then the inode doesn't have an encryption key set up + * so it's irrelevant. If ci_master_key is NULL, then the master key + * was provided via the legacy mechanism of the process-subscribed + * keyrings, so we don't know whether it's been removed or not. + */ + if (!ci || !ci->ci_master_key) + return 0; + mk = ci->ci_master_key->payload.data[0]; + + /* + * Note: since we aren't holding key->sem, the result here can + * immediately become outdated. But there's no correctness problem with + * unnecessarily evicting. Nor is there a correctness problem with not + * evicting while iput() is racing with the key being removed, since + * then the thread removing the key will either evict the inode itself + * or will correctly detect that it wasn't evicted due to the race. + */ + return !is_master_key_secret_present(&mk->mk_secret); +} +EXPORT_SYMBOL(fscrypt_drop_inode); diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index e43c61fcb1125..b6f8832dadba4 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -115,10 +115,12 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *, /* keyring.c */ extern void fscrypt_sb_free(struct super_block *sb); extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg); +extern int fscrypt_ioctl_remove_key(struct file *filp, const void __user *arg); /* keysetup.c */ extern int fscrypt_get_encryption_info(struct inode *); extern void fscrypt_put_encryption_info(struct inode *); +extern int fscrypt_drop_inode(struct inode *inode); /* fname.c */ extern int fscrypt_setup_filename(struct inode *, const struct qstr *, @@ -327,6 +329,12 @@ static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg) return -EOPNOTSUPP; } +static inline int fscrypt_ioctl_remove_key(struct file *filp, + const void __user *arg) +{ + return -EOPNOTSUPP; +} + /* keysetup.c */ static inline int fscrypt_get_encryption_info(struct inode *inode) { @@ -338,6 +346,11 @@ static inline void fscrypt_put_encryption_info(struct inode *inode) return; } +static inline int fscrypt_drop_inode(struct inode *inode) +{ + return 0; +} + /* fname.c */ static inline int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 7bed24632bda7..3302a407131e6 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -65,10 +65,17 @@ struct fscrypt_add_key_arg { __u8 raw[]; }; +/* Struct passed to FS_IOC_REMOVE_ENCRYPTION_KEY */ +struct fscrypt_remove_key_arg { + struct fscrypt_key_specifier key_spec; + __u32 __reserved[6]; +}; + #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) #define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) #define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) #define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg) +#define FS_IOC_REMOVE_ENCRYPTION_KEY _IOW('f', 24, struct fscrypt_remove_key_arg) /**********************************************************************/ From patchwork Tue Apr 2 15:45:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881973 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DEEEF139A for ; Tue, 2 Apr 2019 15:49:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C9C76201F5 for ; Tue, 2 Apr 2019 15:49:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BE69F286A1; Tue, 2 Apr 2019 15:49:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2AAAB201F5 for ; Tue, 2 Apr 2019 15:49:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731578AbfDBPtI (ORCPT ); Tue, 2 Apr 2019 11:49:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:36964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731209AbfDBPsh (ORCPT ); Tue, 2 Apr 2019 11:48:37 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 008572147C; Tue, 2 Apr 2019 15:48:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220115; bh=J8AYoIAYRLSpKetMu795TZzPCxfx2dR17Mj9p52i4FU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gS/jQmACZAyfkQftTDMvUGXhPj/pRx6QscOfJiV6cxnNNL5+7TSfwZoEvn6UFbDuB yu5Mr1Q1xtc3gjVBu1k4F7aspG6FSOiLmRbLncGgydZe88H68DgNjEKLzCTv7IcdiZ dTzqVCcGXy03sSvxf8f/AaetlmqZF5yOPEfHSZT8= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 09/17] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Date: Tue, 2 Apr 2019 08:45:52 -0700 Message-Id: <20190402154600.32432-10-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add a new fscrypt ioctl, FS_IOC_GET_ENCRYPTION_KEY_STATUS. Given a key specified by 'struct fscrypt_key_specifier' (the same way a key is specified for the other fscrypt key management ioctls), it returns status information in a 'struct fscrypt_get_key_status_arg'. The main motivation for this is that applications need to be able to check whether an encrypted directory is "unlocked" or not, so that they can add the key if it is not, and avoid adding the key (which may involve prompting the user for a passphrase) if it already is. It's possible to use some workarounds such as checking whether opening a regular file fails with ENOKEY, or checking whether the filenames "look like gibberish" or not. However, no workaround is usable in all cases. Like the other key management ioctls, the keyrings syscalls may seem at first to be a good fit for this. Unfortunately, they are not. Even if we exposed the keyring ID of the ->s_master_keys keyring and gave everyone Search permission on it (note: currently the keyrings permission system would also allow everyone to "invalidate" the keyring too), the fscrypt keys have an additional state that doesn't map cleanly to the keyrings API: the secret can be removed, but we can be still tracking the files that were using the key, and the removal can be re-attempted or the secret added again. After later patches, some applications will also need a way to determine whether a key was added by the current user vs. by some other user. Reserved fields are included in fscrypt_get_key_status_arg for this and other future extensions. Signed-off-by: Eric Biggers --- fs/crypto/keyring.c | 60 ++++++++++++++++++++++++++++++++++++ include/linux/fscrypt.h | 7 +++++ include/uapi/linux/fscrypt.h | 15 +++++++++ 3 files changed, 82 insertions(+) diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index ee9be002c1490..08e14497c8e30 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -11,6 +11,7 @@ * * - FS_IOC_ADD_ENCRYPTION_KEY: add a key * - FS_IOC_REMOVE_ENCRYPTION_KEY: remove a key + * - FS_IOC_GET_ENCRYPTION_KEY_STATUS: get key status */ #include @@ -482,6 +483,65 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg) } EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key); +/* + * Retrieve the status of an fscrypt master encryption key. + * + * We set ->status to indicate whether the key is absent, present, or + * incompletely removed. "Incompletely removed" means that the master key + * secret has been removed, but some files which had been unlocked with it are + * still in use. This field allows applications to easily determine the state + * of an encrypted directory without using a hack such as trying to open a + * regular file in it (which can confuse the "incompletely removed" state with + * absent or present). + */ +int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_get_key_status_arg arg; + struct key *key; + struct fscrypt_master_key *mk; + int err; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved)); + + key = fscrypt_find_master_key(sb, &arg.key_spec); + if (IS_ERR(key)) { + if (key != ERR_PTR(-ENOKEY)) + return PTR_ERR(key); + arg.status = FSCRYPT_KEY_STATUS_ABSENT; + err = 0; + goto out; + } + mk = key->payload.data[0]; + down_read(&key->sem); + + if (!is_master_key_secret_present(&mk->mk_secret)) { + arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED; + err = 0; + goto out_release_key; + } + + arg.status = FSCRYPT_KEY_STATUS_PRESENT; + err = 0; +out_release_key: + up_read(&key->sem); + key_put(key); +out: + if (!err && copy_to_user(uarg, &arg, sizeof(arg))) + err = -EFAULT; + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status); + int __init fscrypt_init_keyring(void) { return register_key_type(&key_type_fscrypt); diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index b6f8832dadba4..5f251cad255b8 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -116,6 +116,7 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *, extern void fscrypt_sb_free(struct super_block *sb); extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg); extern int fscrypt_ioctl_remove_key(struct file *filp, const void __user *arg); +extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg); /* keysetup.c */ extern int fscrypt_get_encryption_info(struct inode *); @@ -335,6 +336,12 @@ static inline int fscrypt_ioctl_remove_key(struct file *filp, return -EOPNOTSUPP; } +static inline int fscrypt_ioctl_get_key_status(struct file *filp, + void __user *arg) +{ + return -EOPNOTSUPP; +} + /* keysetup.c */ static inline int fscrypt_get_encryption_info(struct inode *inode) { diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 3302a407131e6..042e70a4ff7ee 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -71,11 +71,26 @@ struct fscrypt_remove_key_arg { __u32 __reserved[6]; }; +/* Struct passed to FS_IOC_GET_ENCRYPTION_KEY_STATUS */ +struct fscrypt_get_key_status_arg { + /* input */ + struct fscrypt_key_specifier key_spec; + __u32 __reserved[6]; + + /* output */ +#define FSCRYPT_KEY_STATUS_ABSENT 1 +#define FSCRYPT_KEY_STATUS_PRESENT 2 +#define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED 3 + __u32 status; + __u32 __out_reserved[15]; +}; + #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) #define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) #define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) #define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg) #define FS_IOC_REMOVE_ENCRYPTION_KEY _IOW('f', 24, struct fscrypt_remove_key_arg) +#define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 25, struct fscrypt_get_key_status_arg) /**********************************************************************/ From patchwork Tue Apr 2 15:45:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881987 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6E03C139A for ; Tue, 2 Apr 2019 15:49:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5E068201F5 for ; Tue, 2 Apr 2019 15:49:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 51BC828691; Tue, 2 Apr 2019 15:49:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9BDCA2868C for ; Tue, 2 Apr 2019 15:49:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731641AbfDBPtO (ORCPT ); Tue, 2 Apr 2019 11:49:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:36918 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731229AbfDBPsg (ORCPT ); Tue, 2 Apr 2019 11:48:36 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 73EE7207E0; Tue, 2 Apr 2019 15:48:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220115; bh=rQjvkaYqfwA1ukak/+GujYTQLEQcY6Q9fCJS0mEsfLA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1XMqMESpwfpIJF9Y7IiEAKCVuPLPlNf7/1odPzbSM+u2cMi/q8nb2GxBMEKj2sjCR UsnG5LcxwKmJg4jVuV3GS5zWaGkS8DD4k5I64rO9yM0xpgGdFI9b6hNIrl5u7YNhTy g7dLw7qbxEoRSr/IroQzgmpPgv1FVBxV6TchhwTc= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 10/17] fscrypt: add an HKDF-SHA512 implementation Date: Tue, 2 Apr 2019 08:45:53 -0700 Message-Id: <20190402154600.32432-11-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add an implementation of HKDF (RFC 5869) to fscrypt, for the purpose of deriving additional key material from the fscrypt master keys for v2 encryption policies. HKDF is a key derivation function built on top of HMAC. We choose SHA-512 for the underlying unkeyed hash, and use an "hmac(sha512)" transform allocated from the crypto API. We'll be using this to replace the AES-ECB based KDF currently used to derive the per-file encryption keys. While the AES-ECB based KDF is believed to meet the original security requirements, it is nonstandard and has problems that don't exist in modern KDFs such as HKDF: 1. It's reversible. Given a derived key and nonce, an attacker can easily compute the master key. This is okay if the master key and derived keys are equally hard to compromise, but now we'd like to be more robust against threats such as a derived key being compromised through a timing attack, or a derived key for an in-use file being compromised after the master key has already been removed. 2. It doesn't evenly distribute the entropy from the master key; each 16 input bytes only affects the corresponding 16 output bytes. 3. It isn't easily extensible to deriving other values or keys that are or will be needed, such as per-mode keys (which is what DIRECT_KEY policies really should use, rather than the master key directly as they do now) or a public hash for securely identifying the key (to ensure that an encrypted file cannot be set up with the wrong key). HKDF solves all the above problems. Signed-off-by: Eric Biggers --- fs/crypto/Kconfig | 2 + fs/crypto/Makefile | 1 + fs/crypto/fscrypt_private.h | 15 +++ fs/crypto/hkdf.c | 188 ++++++++++++++++++++++++++++++++++++ 4 files changed, 206 insertions(+) create mode 100644 fs/crypto/hkdf.c diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig index f0de238000c02..c160598a9fe2c 100644 --- a/fs/crypto/Kconfig +++ b/fs/crypto/Kconfig @@ -7,6 +7,8 @@ config FS_ENCRYPTION select CRYPTO_XTS select CRYPTO_CTS select CRYPTO_SHA256 + select CRYPTO_SHA512 + select CRYPTO_HMAC select KEYS help Enable encryption of files and directories. This diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile index accdd622c9083..4977b43479289 100644 --- a/fs/crypto/Makefile +++ b/fs/crypto/Makefile @@ -2,6 +2,7 @@ obj-$(CONFIG_FS_ENCRYPTION) += fscrypto.o fscrypto-y := crypto.o \ fname.o \ + hkdf.o \ hooks.o \ keyring.o \ keysetup.o \ diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index cc1862c9baa1d..e2a65189eb578 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -175,6 +175,21 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); +/* hkdf.c */ + +struct fscrypt_hkdf { + struct crypto_shash *hmac_tfm; +}; + +extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, + unsigned int master_key_size); + +extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, + const u8 *info, unsigned int infolen, + u8 *okm, unsigned int okmlen); + +extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf); + /* keyring.c */ /* diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c new file mode 100644 index 0000000000000..3f9dbf171d967 --- /dev/null +++ b/fs/crypto/hkdf.c @@ -0,0 +1,188 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation + * Function"), aka RFC 5869. See also the original paper (Krawczyk 2010): + * "Cryptographic Extraction and Key Derivation: The HKDF Scheme". + * + * This is used to derive keys from the fscrypt master keys. + * + * Copyright 2019 Google LLC + */ + +#include +#include + +#include "fscrypt_private.h" + +/* + * HKDF supports any unkeyed cryptographic hash algorithm, but fscrypt uses + * SHA-512 because it is reasonably secure and efficient; and since it produces + * a 64-byte digest, deriving an AES-256-XTS key preserves all 64 bytes of + * entropy from the master key and requires only one iteration of HKDF-Expand. + */ +#define HKDF_HMAC_ALG "hmac(sha512)" +#define HKDF_HASHLEN SHA512_DIGEST_SIZE + +/* + * HKDF consists of two steps: + * + * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from + * the input keying material and optional salt. + * 2. HKDF-Expand: expand the pseudorandom key into output keying material of + * any length, parameterized by an application-specific info string. + * + * HKDF-Extract can be skipped if the input is already a pseudorandom key of + * length HKDF_HASHLEN bytes. However, cipher modes other than AES-256-XTS take + * shorter keys, and we don't want to force users of those modes to generate + * unnecessarily long keys. Thus fscrypt still does HKDF-Extract. + * + * HKDF-Extract also supports a salt. Choosing a random salt per input key + * would permit the input key to come from *any* source with sufficient entropy, + * even if it's not distributed uniformly. However, fscrypt doesn't take + * advantage of this because userspace should already provide good pseudorandom + * keys, which makes this unnecessary; also, having to persist a random salt per + * key from kernel mode would pose significant implementation complexity. Thus + * fscrypt uses a fixed salt. But to be slightly more robust against userspace + * (unwisely) reusing the fscrypt keys for another purpose, and to force + * brute-force attacks to target the fscrypt KDF specifically, fscrypt uses + * "fscrypt_hkdf_salt" rather than the default of all 0's defined by RFC 5869. + */ + +#define HKDF_SALT "fscrypt_hkdf_salt" +#define HKDF_SALTLEN CONST_STRLEN(HKDF_SALT) + +/* HKDF-Extract (RFC 5869 section 2.2), see explanation above */ +static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm, + unsigned int ikmlen, u8 prk[HKDF_HASHLEN]) +{ + SHASH_DESC_ON_STACK(desc, hmac_tfm); + int err; + + err = crypto_shash_setkey(hmac_tfm, HKDF_SALT, HKDF_SALTLEN); + if (err) + return err; + + desc->tfm = hmac_tfm; + desc->flags = 0; + err = crypto_shash_digest(desc, ikm, ikmlen, prk); + shash_desc_zero(desc); + return err; +} + +/* + * Compute HKDF-Extract using the given master key as the input keying material, + * and prepare an HMAC transform object keyed by the resulting pseudorandom key. + * + * Afterwards, the keyed HMAC transform object can be used for HKDF-Expand many + * times without having to recompute HKDF-Extract each time. + */ +int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, + unsigned int master_key_size) +{ + struct crypto_shash *hmac_tfm; + u8 prk[HKDF_HASHLEN]; + int err; + + hmac_tfm = crypto_alloc_shash(HKDF_HMAC_ALG, 0, 0); + if (IS_ERR(hmac_tfm)) { + fscrypt_warn(NULL, "error allocating " HKDF_HMAC_ALG ": %ld", + PTR_ERR(hmac_tfm)); + return PTR_ERR(hmac_tfm); + } + + BUG_ON(crypto_shash_digestsize(hmac_tfm) != sizeof(prk)); + + err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk); + if (err) + goto err_free_tfm; + + err = crypto_shash_setkey(hmac_tfm, prk, sizeof(prk)); + if (err) + goto err_free_tfm; + + hkdf->hmac_tfm = hmac_tfm; + goto out; + +err_free_tfm: + crypto_free_shash(hmac_tfm); +out: + memzero_explicit(prk, sizeof(prk)); + return err; +} + +/* + * HKDF-Expand (RFC 5869 section 2.3). This expands the pseudorandom key, which + * was already keyed into 'hkdf->hmac_tfm' by fscrypt_init_hkdf(), into 'okmlen' + * bytes of output keying material parameterized by the application-specific + * 'info' of length 'infolen' bytes, prefixed with the 'context' byte. This is + * thread-safe and may be called by multiple threads in parallel. + * + * ('context' isn't part of the HKDF specification; it's just a prefix fscrypt + * adds to its application-specific info strings to guarantee that it doesn't + * accidentally repeat an info string when using HKDF for different purposes.) + */ +int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, + const u8 *info, unsigned int infolen, + u8 *okm, unsigned int okmlen) +{ + SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm); + unsigned int i; + int err; + const u8 *prev = NULL; + u8 counter = 1; + u8 tmp[HKDF_HASHLEN]; + + if (WARN_ON(okmlen > 255 * HKDF_HASHLEN)) + return -EINVAL; + + desc->tfm = hkdf->hmac_tfm; + desc->flags = 0; + + for (i = 0; i < okmlen; i += HKDF_HASHLEN) { + + err = crypto_shash_init(desc); + if (err) + goto out; + + if (prev) { + err = crypto_shash_update(desc, prev, HKDF_HASHLEN); + if (err) + goto out; + } + + BUILD_BUG_ON(sizeof(context) != 1); + err = crypto_shash_update(desc, &context, 1); + if (err) + goto out; + + err = crypto_shash_update(desc, info, infolen); + if (err) + goto out; + + BUILD_BUG_ON(sizeof(counter) != 1); + if (okmlen - i < HKDF_HASHLEN) { + err = crypto_shash_finup(desc, &counter, 1, tmp); + if (err) + goto out; + memcpy(&okm[i], tmp, okmlen - i); + memzero_explicit(tmp, sizeof(tmp)); + } else { + err = crypto_shash_finup(desc, &counter, 1, &okm[i]); + if (err) + goto out; + } + counter++; + prev = &okm[i]; + } + err = 0; +out: + if (unlikely(err)) + memzero_explicit(okm, okmlen); /* so caller doesn't need to */ + shash_desc_zero(desc); + return err; +} + +void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf) +{ + crypto_free_shash(hkdf->hmac_tfm); +} From patchwork Tue Apr 2 15:45:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881959 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8CDF613B5 for ; Tue, 2 Apr 2019 15:48:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7C0C4201F5 for ; Tue, 2 Apr 2019 15:48:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 702A82868C; Tue, 2 Apr 2019 15:48:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CA7EE286A1 for ; Tue, 2 Apr 2019 15:48:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731479AbfDBPsu (ORCPT ); Tue, 2 Apr 2019 11:48:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:36884 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731252AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E6F12214AF; Tue, 2 Apr 2019 15:48:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220116; bh=Eh+6uvjIsWelOnm/qXiXBB8b0pIjwD2Tr8nyaT2N8lI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YhLlEburvZmh60qGSZnd0QjpsmZpL0F2SpuIlLd+csO8d1rTTkTXwpoh0FSbAgfP/ 68QzKJffkVQ385Uj3pXt6IgoWMcD/nvVCsYfSBtDmkEcAKu5fNpIp9RLxXLcHNeqM4 RH2GmiEzbELceAnRXfF0Pvvca6YcsJ3ThejOKF8c= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 11/17] fscrypt: v2 encryption policy support Date: Tue, 2 Apr 2019 08:45:54 -0700 Message-Id: <20190402154600.32432-12-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add a new fscrypt policy version, "v2". It has the following changes from the original policy version, which we call "v1" (*): - Master keys (the user-provided encryption keys) are only ever used as input to HKDF-SHA512. This is more flexible and less error-prone, and it avoids the quirks and limitations of the AES-128-ECB based KDF. Three classes of cryptographically isolated subkeys are defined: - Per-file keys, like used in v1 policies except for the new KDF. - Per-mode keys. These implement the semantics of the DIRECT_KEY flag, which for v1 policies made the master key be used directly. - Key identifiers (see below). - Each master key is identified by a 16-byte master_key_identifier, which is derived from the key itself using HKDF-SHA512. This prevents users from associating the wrong key with an encrypted file or directory. This was easily possible with v1 policies, which identified the key by an arbitrary 8-byte master_key_descriptor. - The key must be provided in the filesystem-level keyring, not in a process-subscribed keyring. The following UAPI additions are made: - The existing ioctl FS_IOC_SET_ENCRYPTION_POLICY can now be passed a fscrypt_policy_v2 to set a v2 encryption policy. It's disambiguated from fscrypt_policy/fscrypt_policy_v1 by the version code prefix. - A new ioctl FS_IOC_GET_ENCRYPTION_POLICY_EX is added. It allows getting the v1 or v2 encryption policy of an encrypted file or directory. The existing FS_IOC_GET_ENCRYPTION_POLICY ioctl could not be used because it did not have a way for userspace to indicate which policy structure is expected. The new ioctl includes a size field, so it is extensible to future fscrypt policy versions. - The ioctls FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY, and FS_IOC_GET_ENCRYPTION_KEY_STATUS now support managing keys for v2 encryption policies. Such keys are kept logically separate from keys for v1 encryption policies, and are identified by 'identifier' rather than by 'descriptor'. The 'identifier' need not be provided when adding a key, since the kernel will calculate it anyway. This patch temporarily keeps adding/removing v2 policy keys behind the same permission check done for adding/removing v1 policy keys: capable(CAP_SYS_ADMIN). However, the next patch will carefully take advantage of the cryptographically secure master_key_identifier to allow non-root users to add/remove v2 policy keys, thus providing a full replacement for v1 policies. (*) Actually, in the API fscrypt_policy::version is 0 while on-disk fscrypt_context::format is 1. But I believe it makes the most sense to advance both to '2' to have them be in sync, and to consider the numbering to start at 1 except for the API quirk. Signed-off-by: Eric Biggers --- fs/crypto/crypto.c | 3 +- fs/crypto/fname.c | 3 +- fs/crypto/fscrypt_private.h | 182 ++++++++++++++--- fs/crypto/keyring.c | 37 +++- fs/crypto/keysetup.c | 174 ++++++++++++---- fs/crypto/keysetup_legacy.c | 18 +- fs/crypto/policy.c | 382 +++++++++++++++++++++++++---------- include/linux/fscrypt.h | 9 +- include/uapi/linux/fscrypt.h | 42 +++- 9 files changed, 667 insertions(+), 183 deletions(-) diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 8726c4e940773..7abc6695fa4d9 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -26,7 +26,6 @@ #include #include #include -#include #include #include "fscrypt_private.h" @@ -139,7 +138,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, memset(iv, 0, ci->ci_mode->ivsize); iv->lblk_num = cpu_to_le64(lblk_num); - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + if (fscrypt_is_direct_key_policy(&ci->ci_policy)) memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE); if (ci->ci_essiv_tfm != NULL) diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 37c26ad36d0e3..57e0caba9d126 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -186,7 +186,8 @@ static int digest_decode(const char *src, int len, char *dst) bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret) { - int padding = 4 << (inode->i_crypt_info->ci_flags & + const struct fscrypt_info *ci = inode->i_crypt_info; + int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) & FSCRYPT_POLICY_FLAGS_PAD_MASK); u32 encrypted_len; diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index e2a65189eb578..9591f5fd72b33 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -20,27 +20,127 @@ #define FSCRYPT_MIN_KEY_SIZE 16 -/** - * Encryption context for inode - * - * Protector format: - * 1 byte: Protector format (1 = this version) - * 1 byte: File contents encryption mode - * 1 byte: File names encryption mode - * 1 byte: Flags - * 8 bytes: Master Key descriptor - * 16 bytes: Encryption Key derivation nonce - */ -struct fscrypt_context { - u8 format; +#define FSCRYPT_CONTEXT_V1 1 +#define FSCRYPT_CONTEXT_V2 2 + +struct fscrypt_context_v1 { + u8 version; /* FSCRYPT_CONTEXT_V1 */ u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; -} __packed; +}; + +struct fscrypt_context_v2 { + u8 version; /* FSCRYPT_CONTEXT_V2 */ + u8 contents_encryption_mode; + u8 filenames_encryption_mode; + u8 flags; + u8 __reserved[4]; + u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; +}; + +/** + * fscrypt_context - the encryption context of an inode + * + * This is the on-disk equivalent of an fscrypt_policy, stored alongside each + * encrypted file usually in a hidden extended attribute. It contains the + * fields from the fscrypt_policy, in order to identify the encryption algorithm + * and key with which the file is encrypted. It also contains a nonce that was + * randomly generated by fscrypt itself; this is used as KDF input or as a tweak + * to cause different files to be encrypted differently. + */ +union fscrypt_context { + u8 version; + struct fscrypt_context_v1 v1; + struct fscrypt_context_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_context based on its version + * number, or 0 if the context version is unrecognized. + */ +static inline int fscrypt_context_size(const union fscrypt_context *ctx) +{ + switch (ctx->version) { + case FSCRYPT_CONTEXT_V1: + BUILD_BUG_ON(sizeof(ctx->v1) != 28); + return sizeof(ctx->v1); + case FSCRYPT_CONTEXT_V2: + BUILD_BUG_ON(sizeof(ctx->v2) != 40); + return sizeof(ctx->v2); + } + return 0; +} + +#undef fscrypt_policy +union fscrypt_policy { + __u8 version; + struct fscrypt_policy_v1 v1; + struct fscrypt_policy_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_policy based on its version + * number, or 0 if the policy version is unrecognized. + */ +static inline int fscrypt_policy_size(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return sizeof(policy->v1); + case FSCRYPT_POLICY_V2: + return sizeof(policy->v2); + } + return 0; +} -#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1 +/* Return the contents encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_contents_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.contents_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.contents_encryption_mode; + } + BUG(); +} + +/* Return the filenames encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_fnames_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.filenames_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.filenames_encryption_mode; + } + BUG(); +} + +/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */ +static inline u8 +fscrypt_policy_flags(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.flags; + case FSCRYPT_POLICY_V2: + return policy->v2.flags; + } + BUG(); +} + +static inline bool +fscrypt_is_direct_key_policy(const union fscrypt_policy *policy) +{ + return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY; +} /** * For encrypted symlinks, the ciphertext length is stored at the beginning @@ -70,8 +170,8 @@ struct fscrypt_info { struct crypto_cipher *ci_essiv_tfm; /* - * Encryption mode used for this inode. It corresponds to either - * ci_data_mode or ci_filename_mode, depending on the inode type. + * Encryption mode used for this inode. It corresponds to either the + * contents or filenames encryption mode, depending on the inode type. */ struct fscrypt_mode *ci_mode; @@ -97,11 +197,10 @@ struct fscrypt_info { */ struct fscrypt_direct_key *ci_direct_key; - /* fields from the fscrypt_context */ - u8 ci_data_mode; - u8 ci_filename_mode; - u8 ci_flags; - u8 ci_master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + /* The encryption policy used by this inode */ + union fscrypt_policy ci_policy; + + /* This inode's nonce, copied from the fscrypt_context */ u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; @@ -184,6 +283,17 @@ struct fscrypt_hkdf { extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, unsigned int master_key_size); +/* + * The list of contexts in which fscrypt uses HKDF. These values are used as + * the first byte of the HKDF application-specific info string to guarantee that + * info strings are never repeated between contexts. This ensures that all HKDF + * outputs are unique and cryptographically isolated, i.e. knowledge of one + * output doesn't reveal another. + */ +#define HKDF_CONTEXT_KEY_IDENTIFIER 1 +#define HKDF_CONTEXT_PER_FILE_KEY 2 +#define HKDF_CONTEXT_PER_MODE_KEY 3 + extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, const u8 *info, unsigned int infolen, u8 *okm, unsigned int okmlen); @@ -197,10 +307,16 @@ extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf); */ struct fscrypt_master_key_secret { - /* Size of the raw key in bytes */ + /* + * For v2 policy keys: HKDF context keyed by this master key. + * For v1 policy keys: not set (hkdf.hmac_tfm == NULL). + */ + struct fscrypt_hkdf hkdf; + + /* Size of the raw key in bytes. Set even if ->raw isn't set. */ u32 size; - /* The raw key */ + /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */ u8 raw[FSCRYPT_MAX_KEY_SIZE]; } __randomize_layout; @@ -226,7 +342,12 @@ struct fscrypt_master_key { */ struct fscrypt_master_key_secret mk_secret; - /* Arbitrary key descriptor which was assigned by userspace */ + /* + * For v1 policy keys: an arbitrary key descriptor which was assigned by + * userspace (->descriptor). + * + * For v2 policy keys: a cryptographic hash of this key (->identifier). + */ struct fscrypt_key_specifier mk_spec; /* @@ -245,6 +366,9 @@ struct fscrypt_master_key { struct list_head mk_decrypted_inodes; spinlock_t mk_decrypted_inodes_lock; + /* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */ + struct crypto_skcipher *mk_mode_keys[__FSCRYPT_MODE_MAX + 1]; + } __randomize_layout; static inline bool @@ -302,5 +426,13 @@ extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings( struct fscrypt_info *ci); +/* policy.c */ + +extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2); +extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u); +extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u, + const union fscrypt_context *ctx_u, + int ctx_size); #endif /* _FSCRYPT_PRIVATE_H */ diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 08e14497c8e30..fe1b003975c4f 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -14,6 +14,7 @@ * - FS_IOC_GET_ENCRYPTION_KEY_STATUS: get key status */ +#include #include #include @@ -21,6 +22,7 @@ static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret) { + fscrypt_destroy_hkdf(&secret->hkdf); memzero_explicit(secret, sizeof(*secret)); } @@ -33,7 +35,13 @@ static void move_master_key_secret(struct fscrypt_master_key_secret *dst, static void free_master_key(struct fscrypt_master_key *mk) { + size_t i; + wipe_master_key_secret(&mk->mk_secret); + + for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++) + crypto_free_skcipher(mk->mk_mode_keys[i]); + kzfree(mk); } @@ -42,6 +50,8 @@ static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec) switch (spec->type) { case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: return FSCRYPT_KEY_DESCRIPTOR_SIZE; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + return FSCRYPT_KEY_IDENTIFIER_SIZE; } return 0; } @@ -115,7 +125,7 @@ static struct key *search_fscrypt_keyring(struct key *keyring, #define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id)) -#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1) +#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1) static void format_fs_keyring_description( char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], @@ -319,6 +329,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) if (!capable(CAP_SYS_ADMIN)) goto out_wipe_secret; + if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { + err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size); + if (err) + goto out_wipe_secret; + + /* + * Now that the HKDF context is initialized, the raw key is no + * longer needed. + */ + memzero_explicit(secret.raw, sizeof(secret.raw)); + + /* Calculate the key identifier and return it to userspace. */ + err = fscrypt_hkdf_expand(&secret.hkdf, + HKDF_CONTEXT_KEY_IDENTIFIER, + NULL, 0, arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + if (err) + goto out_wipe_secret; + err = -EFAULT; + if (copy_to_user(uarg->key_spec.u.identifier, + arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE)) + goto out_wipe_secret; + } + err = add_master_key(sb, &secret, &arg.key_spec); out_wipe_secret: wipe_master_key_secret(&secret); diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index f8fb115c63ab9..c81447a438ea9 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -52,21 +52,14 @@ static struct fscrypt_mode available_modes[] = { }; static struct fscrypt_mode * -select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) +select_encryption_mode(const union fscrypt_policy *policy, + const struct inode *inode) { - if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { - fscrypt_warn(inode->i_sb, - "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", - inode->i_ino, ci->ci_data_mode, - ci->ci_filename_mode); - return ERR_PTR(-EINVAL); - } - if (S_ISREG(inode->i_mode)) - return &available_modes[ci->ci_data_mode]; + return &available_modes[fscrypt_policy_contents_mode(policy)]; if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) - return &available_modes[ci->ci_filename_mode]; + return &available_modes[fscrypt_policy_fnames_mode(policy)]; WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", inode->i_ino, (inode->i_mode & S_IFMT)); @@ -208,6 +201,83 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) return 0; } +static int setup_per_mode_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + u8 mode_num = ci->ci_mode - available_modes; + struct crypto_skcipher **tfm_p; + struct crypto_skcipher *tfm; + u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys))) + return -EINVAL; + tfm_p = &mk->mk_mode_keys[mode_num]; +retry: + /* pairs with cmpxchg_release() below */ + tfm = smp_load_acquire(tfm_p); + if (likely(tfm != NULL)) + goto done; + + BUILD_BUG_ON(sizeof(mode_num) != 1); + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_MODE_KEY, + &mode_num, sizeof(mode_num), + mode_key, ci->ci_mode->keysize); + if (err) + return err; + tfm = fscrypt_allocate_skcipher(ci->ci_mode, mode_key, ci->ci_inode); + memzero_explicit(mode_key, ci->ci_mode->keysize); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + + /* pairs with smp_load_acquire() above */ + if (cmpxchg_release(tfm_p, NULL, tfm) != NULL) { + crypto_free_skcipher(tfm); + goto retry; + } +done: + ci->ci_ctfm = tfm; + return 0; +} + +static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + /* + * DIRECT_KEY: instead of deriving per-file keys, the per-file + * nonce will be included in all the IVs. But unlike v1 + * policies, for v2 policies in this case we don't encrypt with + * the master key directly but rather derive a per-mode key. + * This ensures that the master key is consistently used only + * for HKDF, avoiding key reuse issues. + */ + if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) { + fscrypt_warn(ci->ci_inode->i_sb, + "direct key flag not allowed with %s", + ci->ci_mode->friendly_name); + return -EINVAL; + } + return setup_per_mode_key(ci, mk); + } + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_FILE_KEY, + ci->ci_nonce, + FS_KEY_DERIVATION_NONCE_SIZE, + derived_key, ci->ci_mode->keysize); + if (err) + return err; + + err = fscrypt_set_derived_key(ci, derived_key); + memzero_explicit(derived_key, ci->ci_mode->keysize); + return err; +} + /* * Find the master key, then set up the inode's actual encryption key. * @@ -226,15 +296,30 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, struct fscrypt_key_specifier mk_spec; int err; - mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; - memcpy(mk_spec.u.descriptor, ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); + if (ci->ci_policy.version == FSCRYPT_POLICY_V1) { + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; + memcpy(mk_spec.u.descriptor, + ci->ci_policy.v1.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + } else { + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; + memcpy(mk_spec.u.identifier, + ci->ci_policy.v2.master_key_identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + } key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec); if (IS_ERR(key)) { - if (key != ERR_PTR(-ENOKEY)) + if (key != ERR_PTR(-ENOKEY) || + ci->ci_policy.version != FSCRYPT_POLICY_V1) return PTR_ERR(key); + /* + * As a legacy fallback for v1 policies, search for the key in + * the current task's subscribed keyrings too. Don't move this + * to before the search of ->s_master_keys, since users + * shouldn't be able to override filesystem-level keys. + */ return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); } @@ -247,6 +332,12 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, goto out_release_key; } + /* + * Require that the master key be at least as long as the derived key. + * Otherwise, the derived key cannot possibly contain as much entropy as + * that required by the encryption mode it will be used for. For v1 + * policies it's also required for the KDF to work at all. + */ if (mk->mk_secret.size < ci->ci_mode->keysize) { fscrypt_warn(NULL, "key with description '%s' is too short (got %u bytes, need %u+ bytes)", @@ -256,7 +347,10 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, goto out_release_key; } - err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + if (ci->ci_policy.version == FSCRYPT_POLICY_V1) + err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + else + err = fscrypt_setup_v2_file_key(ci, mk); if (err) goto out_release_key; @@ -278,7 +372,8 @@ static void put_crypt_info(struct fscrypt_info *ci) if (ci->ci_direct_key) { fscrypt_put_direct_key(ci->ci_direct_key); - } else { + } else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) && + !fscrypt_is_direct_key_policy(&ci->ci_policy)) { crypto_free_skcipher(ci->ci_ctfm); crypto_free_cipher(ci->ci_essiv_tfm); } @@ -308,7 +403,7 @@ static void put_crypt_info(struct fscrypt_info *ci) int fscrypt_get_encryption_info(struct inode *inode) { struct fscrypt_info *crypt_info; - struct fscrypt_context ctx; + union fscrypt_context ctx; struct fscrypt_mode *mode; struct key *master_key = NULL; int res; @@ -327,35 +422,40 @@ int fscrypt_get_encryption_info(struct inode *inode) return res; /* Fake up a context for an unencrypted directory */ memset(&ctx, 0, sizeof(ctx)); - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, + ctx.version = FSCRYPT_CONTEXT_V1; + ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.v1.master_key_descriptor, 0x42, FSCRYPT_KEY_DESCRIPTOR_SIZE); - } else if (res != sizeof(ctx)) { - return -EINVAL; + res = sizeof(ctx.v1); } - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) - return -EINVAL; - - if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) - return -EINVAL; - crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); if (!crypt_info) return -ENOMEM; crypt_info->ci_inode = inode; - crypt_info->ci_flags = ctx.flags; - crypt_info->ci_data_mode = ctx.contents_encryption_mode; - crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; - memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res); + if (res) + goto out; + + if (ctx.version == FSCRYPT_CONTEXT_V1) + memcpy(crypt_info->ci_nonce, ctx.v1.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + else + memcpy(crypt_info->ci_nonce, ctx.v2.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + + if (!fscrypt_supported_policy(&crypt_info->ci_policy)) { + fscrypt_warn(inode->i_sb, + "inode %lu uses unsupported encryption policy", + inode->i_ino); + res = -EINVAL; + goto out; + } - mode = select_encryption_mode(crypt_info, inode); + mode = select_encryption_mode(&crypt_info->ci_policy, inode); if (IS_ERR(mode)) { res = PTR_ERR(mode); goto out; diff --git a/fs/crypto/keysetup_legacy.c b/fs/crypto/keysetup_legacy.c index 407daa0b64d82..1ec420b189f0f 100644 --- a/fs/crypto/keysetup_legacy.c +++ b/fs/crypto/keysetup_legacy.c @@ -189,12 +189,13 @@ find_or_insert_direct_key(struct fscrypt_direct_key *to_insert, */ BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); - memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); + memcpy(&hash_key, ci->ci_policy.v1.master_key_descriptor, + sizeof(hash_key)); spin_lock(&fscrypt_direct_keys_lock); hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) { - if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) + if (memcmp(ci->ci_policy.v1.master_key_descriptor, + dk->dk_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) continue; if (ci->ci_mode != dk->dk_mode) continue; @@ -237,7 +238,7 @@ fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key) dk->dk_ctfm = NULL; goto err_free_dk; } - memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor, + memcpy(dk->dk_descriptor, ci->ci_policy.v1.master_key_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE); memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize); @@ -262,7 +263,8 @@ static int setup_v1_file_key_direct(struct fscrypt_info *ci, return -EINVAL; } - if (ci->ci_data_mode != ci->ci_filename_mode) { + if (ci->ci_policy.v1.contents_encryption_mode != + ci->ci_policy.v1.filenames_encryption_mode) { fscrypt_warn(ci->ci_inode->i_sb, "direct key flag not allowed with different contents and filenames modes"); return -EINVAL; @@ -308,7 +310,7 @@ static int setup_v1_file_key_derived(struct fscrypt_info *ci, int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key) { - if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + if (ci->ci_policy.v1.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) return setup_v1_file_key_direct(ci, raw_master_key); else return setup_v1_file_key_derived(ci, raw_master_key); @@ -321,11 +323,11 @@ int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci) int err; key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, - ci->ci_master_key_descriptor, + ci->ci_policy.v1.master_key_descriptor, ci->ci_mode->keysize, &payload); if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) { key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix, - ci->ci_master_key_descriptor, + ci->ci_policy.v1.master_key_descriptor, ci->ci_mode->keysize, &payload); } if (IS_ERR(key)) diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 1e0563cea1a56..912ff1d030796 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -5,8 +5,9 @@ * Copyright (C) 2015, Google, Inc. * Copyright (C) 2015, Motorola Mobility. * - * Written by Michael Halcrow, 2015. + * Originally written by Michael Halcrow, 2015. * Modified by Jaegeuk Kim, 2015. + * Modified by Eric Biggers, 2019 for v2 policy support. */ #include @@ -14,84 +15,263 @@ #include #include "fscrypt_private.h" -/* - * check whether an encryption policy is consistent with an encryption context +/** + * fscrypt_policies_equal - check whether two encryption policies are the same + * + * Return: %true if equal, else %false + */ +bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2) +{ + if (policy1->version != policy2->version) + return false; + + return !memcmp(policy1, policy2, fscrypt_policy_size(policy1)); +} + +/** + * fscrypt_supported_policy - check whether an encryption policy is supported + * + * Given an encryption policy, check whether all its encryption modes and other + * settings are supported by this kernel. (But we don't currently don't check + * for crypto API support here, so attempting to use an algorithm not configured + * into the crypto API will still fail later.) + * + * Return: %true if supported, else %false */ -static bool is_encryption_context_consistent_with_policy( - const struct fscrypt_context *ctx, - const struct fscrypt_policy *policy) +bool fscrypt_supported_policy(const union fscrypt_policy *policy_u) { - return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && - (ctx->flags == policy->flags) && - (ctx->contents_encryption_mode == - policy->contents_encryption_mode) && - (ctx->filenames_encryption_mode == - policy->filenames_encryption_mode); + switch (policy_u->version) { + case FSCRYPT_POLICY_V1: { + const struct fscrypt_policy_v1 *policy = &policy_u->v1; + + if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, + policy->filenames_encryption_mode)) + return false; + + if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) + return false; + + return true; + } + case FSCRYPT_POLICY_V2: { + const struct fscrypt_policy_v2 *policy = &policy_u->v2; + + if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, + policy->filenames_encryption_mode)) + return false; + + if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) + return false; + + if (memchr_inv(policy->__reserved, 0, + sizeof(policy->__reserved))) + return false; + + return true; + } + } + return false; } -static int create_encryption_context_from_policy(struct inode *inode, - const struct fscrypt_policy *policy) +/** + * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy + * + * Create an fscrypt_context for an inode that is being assigned the given + * encryption policy. A new nonce is randomly generated. + * + * Return: the size of the new context in bytes. + */ +static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u, + const union fscrypt_policy *policy_u) { - struct fscrypt_context ctx; + memset(ctx_u, 0, sizeof(*ctx_u)); + + switch (policy_u->version) { + case FSCRYPT_POLICY_V1: { + const struct fscrypt_policy_v1 *policy = &policy_u->v1; + struct fscrypt_context_v1 *ctx = &ctx_u->v1; + + ctx->version = FSCRYPT_CONTEXT_V1; + ctx->contents_encryption_mode = + policy->contents_encryption_mode; + ctx->filenames_encryption_mode = + policy->filenames_encryption_mode; + ctx->flags = policy->flags; + memcpy(ctx->master_key_descriptor, + policy->master_key_descriptor, + sizeof(ctx->master_key_descriptor)); + get_random_bytes(ctx->nonce, sizeof(ctx->nonce)); + return sizeof(*ctx); + } + case FSCRYPT_POLICY_V2: { + const struct fscrypt_policy_v2 *policy = &policy_u->v2; + struct fscrypt_context_v2 *ctx = &ctx_u->v2; + + ctx->version = FSCRYPT_CONTEXT_V2; + ctx->contents_encryption_mode = + policy->contents_encryption_mode; + ctx->filenames_encryption_mode = + policy->filenames_encryption_mode; + ctx->flags = policy->flags; + memcpy(ctx->master_key_identifier, + policy->master_key_identifier, + sizeof(ctx->master_key_identifier)); + get_random_bytes(ctx->nonce, sizeof(ctx->nonce)); + return sizeof(*ctx); + } + } + BUG(); +} - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); +/** + * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy + * + * Given an fscrypt_context, build the corresponding fscrypt_policy. + * + * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized + * version number or size. + * + * This does *not* validate the settings within the policy itself, e.g. the + * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that. + */ +int fscrypt_policy_from_context(union fscrypt_policy *policy_u, + const union fscrypt_context *ctx_u, + int ctx_size) +{ + memset(policy_u, 0, sizeof(*policy_u)); - if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, - policy->filenames_encryption_mode)) + if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u)) return -EINVAL; - if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) + switch (ctx_u->version) { + case FSCRYPT_CONTEXT_V1: { + const struct fscrypt_context_v1 *ctx = &ctx_u->v1; + struct fscrypt_policy_v1 *policy = &policy_u->v1; + + policy->version = FSCRYPT_POLICY_V1; + policy->contents_encryption_mode = + ctx->contents_encryption_mode; + policy->filenames_encryption_mode = + ctx->filenames_encryption_mode; + policy->flags = ctx->flags; + memcpy(policy->master_key_descriptor, + ctx->master_key_descriptor, + sizeof(policy->master_key_descriptor)); + return 0; + } + case FSCRYPT_CONTEXT_V2: { + const struct fscrypt_context_v2 *ctx = &ctx_u->v2; + struct fscrypt_policy_v2 *policy = &policy_u->v2; + + policy->version = FSCRYPT_POLICY_V2; + policy->contents_encryption_mode = + ctx->contents_encryption_mode; + policy->filenames_encryption_mode = + ctx->filenames_encryption_mode; + policy->flags = ctx->flags; + memcpy(policy->__reserved, ctx->__reserved, + sizeof(policy->__reserved)); + memcpy(policy->master_key_identifier, + ctx->master_key_identifier, + sizeof(policy->master_key_identifier)); + return 0; + } + } + /* unreachable */ + return -EINVAL; +} + +/* Retrieve an inode's encryption policy */ +static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy) +{ + union fscrypt_context ctx; + int ret; + + if (inode->i_crypt_info) { + /* key available, use the cached policy */ + *policy = inode->i_crypt_info->ci_policy; + return 0; + } + + if (!IS_ENCRYPTED(inode)) + return -ENODATA; + + ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (ret < 0) + return (ret == -ERANGE) ? -EINVAL : ret; + + return fscrypt_policy_from_context(policy, &ctx, ret); +} + +static int set_encryption_policy(struct inode *inode, + const union fscrypt_policy *policy) +{ + union fscrypt_context ctx; + int ctxsize; + + if (!fscrypt_supported_policy(policy)) return -EINVAL; - ctx.contents_encryption_mode = policy->contents_encryption_mode; - ctx.filenames_encryption_mode = policy->filenames_encryption_mode; - ctx.flags = policy->flags; - BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE); - get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + if (policy->version == FSCRYPT_POLICY_V1) { + /* + * The original encryption policy version provided no way of + * verifying that the correct master key was supplied, which was + * insecure in scenarios where multiple users have access to the + * same encrypted files (even just read-only access). The new + * encryption policy version fixes this and also implies use of + * an improved key derivation function and allows non-root users + * to securely remove keys. So as long as compatibility with + * old kernels isn't required, it is recommended to use the new + * policy version for all new encrypted directories. + */ + pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n", + current->comm, current->pid); + } + + ctxsize = fscrypt_new_context_from_policy(&ctx, policy); - return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL); + return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL); } int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) { - struct fscrypt_policy policy; + union fscrypt_policy policy; + union fscrypt_policy existing_policy; struct inode *inode = file_inode(filp); + int size; int ret; - struct fscrypt_context ctx; - if (copy_from_user(&policy, arg, sizeof(policy))) + if (copy_from_user(&policy, arg, sizeof(u8))) + return -EFAULT; + + size = fscrypt_policy_size(&policy); + if (size <= 0) + return -EINVAL; + + if (copy_from_user((u8 *)&policy + 1, arg + 1, size - 1)) return -EFAULT; if (!inode_owner_or_capable(inode)) return -EACCES; - if (policy.version != 0) - return -EINVAL; - ret = mnt_want_write_file(filp); if (ret) return ret; inode_lock(inode); - ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + ret = fscrypt_get_policy(inode, &existing_policy); if (ret == -ENODATA) { if (!S_ISDIR(inode->i_mode)) ret = -ENOTDIR; else if (!inode->i_sb->s_cop->empty_dir(inode)) ret = -ENOTEMPTY; else - ret = create_encryption_context_from_policy(inode, - &policy); - } else if (ret == sizeof(ctx) && - is_encryption_context_consistent_with_policy(&ctx, - &policy)) { - /* The file already uses the same encryption policy. */ - ret = 0; - } else if (ret >= 0 || ret == -ERANGE) { + ret = set_encryption_policy(inode, &policy); + } else if (ret == -EINVAL || + (ret == 0 && !fscrypt_policies_equal(&policy, + &existing_policy))) { /* The file already uses a different encryption policy. */ ret = -EEXIST; } @@ -103,37 +283,55 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) } EXPORT_SYMBOL(fscrypt_ioctl_set_policy); +/* Original ioctl version; can only get the original policy version */ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) { - struct inode *inode = file_inode(filp); - struct fscrypt_context ctx; - struct fscrypt_policy policy; - int res; + union fscrypt_policy policy; + int err; - if (!IS_ENCRYPTED(inode)) - return -ENODATA; + err = fscrypt_get_policy(file_inode(filp), &policy); + if (err) + return err; - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0 && res != -ERANGE) - return res; - if (res != sizeof(ctx)) - return -EINVAL; - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + if (policy.version != FSCRYPT_POLICY_V1) return -EINVAL; - policy.version = 0; - policy.contents_encryption_mode = ctx.contents_encryption_mode; - policy.filenames_encryption_mode = ctx.filenames_encryption_mode; - policy.flags = ctx.flags; - memcpy(policy.master_key_descriptor, ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - - if (copy_to_user(arg, &policy, sizeof(policy))) + if (copy_to_user(arg, &policy, sizeof(policy.v1))) return -EFAULT; return 0; } EXPORT_SYMBOL(fscrypt_ioctl_get_policy); +/* Extended ioctl version; can get policies of any version */ +int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *_uarg) +{ + struct fscrypt_get_policy_ex_arg __user *uarg = _uarg; + struct fscrypt_get_policy_ex_arg arg; + union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy; + u64 avail_size; + int err; + + BUILD_BUG_ON(sizeof(arg.policy) != sizeof(union fscrypt_policy)); + BUILD_BUG_ON(sizeof(arg.policy_size) != + offsetof(struct fscrypt_get_policy_ex_arg, policy)); + + err = fscrypt_get_policy(file_inode(filp), policy); + if (err) + return err; + arg.policy_size = fscrypt_policy_size(policy); + + if (get_user(avail_size, &uarg->policy_size)) + return -EFAULT; + + if (avail_size < arg.policy_size) + return -EOVERFLOW; + + if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + arg.policy_size)) + return -EFAULT; + return 0; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex); + /** * fscrypt_has_permitted_context() - is a file's encryption policy permitted * within its directory? @@ -155,10 +353,8 @@ EXPORT_SYMBOL(fscrypt_ioctl_get_policy); */ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { - const struct fscrypt_operations *cops = parent->i_sb->s_cop; - const struct fscrypt_info *parent_ci, *child_ci; - struct fscrypt_context parent_ctx, child_ctx; - int res; + union fscrypt_policy parent_policy, child_policy; + int err; /* No restrictions on file types which are never encrypted */ if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) && @@ -188,41 +384,22 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) * In any case, if an unexpected error occurs, fall back to "forbidden". */ - res = fscrypt_get_encryption_info(parent); - if (res) + err = fscrypt_get_encryption_info(parent); + if (err) return 0; - res = fscrypt_get_encryption_info(child); - if (res) + err = fscrypt_get_encryption_info(child); + if (err) return 0; - parent_ci = parent->i_crypt_info; - child_ci = child->i_crypt_info; - - if (parent_ci && child_ci) { - return memcmp(parent_ci->ci_master_key_descriptor, - child_ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && - (parent_ci->ci_data_mode == child_ci->ci_data_mode) && - (parent_ci->ci_filename_mode == - child_ci->ci_filename_mode) && - (parent_ci->ci_flags == child_ci->ci_flags); - } - res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx)); - if (res != sizeof(parent_ctx)) + err = fscrypt_get_policy(parent, &parent_policy); + if (err) return 0; - res = cops->get_context(child, &child_ctx, sizeof(child_ctx)); - if (res != sizeof(child_ctx)) + err = fscrypt_get_policy(child, &child_policy); + if (err) return 0; - return memcmp(parent_ctx.master_key_descriptor, - child_ctx.master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 && - (parent_ctx.contents_encryption_mode == - child_ctx.contents_encryption_mode) && - (parent_ctx.filenames_encryption_mode == - child_ctx.filenames_encryption_mode) && - (parent_ctx.flags == child_ctx.flags); + return fscrypt_policies_equal(&parent_policy, &child_policy); } EXPORT_SYMBOL(fscrypt_has_permitted_context); @@ -238,7 +415,8 @@ EXPORT_SYMBOL(fscrypt_has_permitted_context); int fscrypt_inherit_context(struct inode *parent, struct inode *child, void *fs_data, bool preload) { - struct fscrypt_context ctx; + union fscrypt_context ctx; + int ctxsize; struct fscrypt_info *ci; int res; @@ -250,16 +428,10 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, if (ci == NULL) return -ENOKEY; - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = ci->ci_data_mode; - ctx.filenames_encryption_mode = ci->ci_filename_mode; - ctx.flags = ci->ci_flags; - memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor, - FSCRYPT_KEY_DESCRIPTOR_SIZE); - get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy); + BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE); - res = parent->i_sb->s_cop->set_context(child, &ctx, - sizeof(ctx), fs_data); + res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data); if (res) return res; return preload ? fscrypt_get_encryption_info(child): 0; diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 5f251cad255b8..3ed02a0849db6 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -42,7 +42,7 @@ struct fscrypt_name { #define fname_len(p) ((p)->disk_name.len) /* Maximum value for the third parameter of fscrypt_operations.set_context(). */ -#define FSCRYPT_SET_CONTEXT_MAX_SIZE 28 +#define FSCRYPT_SET_CONTEXT_MAX_SIZE 40 #ifdef CONFIG_FS_ENCRYPTION /* @@ -109,6 +109,7 @@ extern void fscrypt_restore_control_page(struct page *); /* policy.c */ extern int fscrypt_ioctl_set_policy(struct file *, const void __user *); extern int fscrypt_ioctl_get_policy(struct file *, void __user *); +extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool); @@ -306,6 +307,12 @@ static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) return -EOPNOTSUPP; } +static inline int fscrypt_ioctl_get_policy_ex(struct file *filp, + void __user *arg) +{ + return -EOPNOTSUPP; +} + static inline int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 042e70a4ff7ee..26879e669dfa0 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -8,7 +8,6 @@ * File system encryption support */ /* Policy provided via an ioctl on the topmost directory */ -#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 /* Encryption policy flags */ #define FSCRYPT_POLICY_FLAGS_PAD_4 0x00 @@ -16,7 +15,7 @@ #define FSCRYPT_POLICY_FLAGS_PAD_16 0x02 #define FSCRYPT_POLICY_FLAGS_PAD_32 0x03 #define FSCRYPT_POLICY_FLAGS_PAD_MASK 0x03 -#define FSCRYPT_POLICY_FLAG_DIRECT_KEY 0x04 /* use master key directly */ +#define FSCRYPT_POLICY_FLAG_DIRECT_KEY 0x04 #define FSCRYPT_POLICY_FLAGS_VALID 0x07 /* Encryption algorithms */ @@ -25,14 +24,24 @@ #define FSCRYPT_MODE_AES_128_CBC 5 #define FSCRYPT_MODE_AES_128_CTS 6 #define FSCRYPT_MODE_ADIANTUM 9 +#define __FSCRYPT_MODE_MAX 9 -struct fscrypt_policy { +/* + * Legacy policy version; ad-hoc KDF and no key verification. + * For new encrypted directories, use fscrypt_policy_v2 instead. + * + * Careful: the .version field for this is actually 0, not 1. + */ +#define FSCRYPT_POLICY_V1 0 +#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 +struct fscrypt_policy_v1 { __u8 version; __u8 contents_encryption_mode; __u8 filenames_encryption_mode; __u8 flags; __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; }; +#define fscrypt_policy fscrypt_policy_v1 /* * Process-subscribed "logon" key description prefix and payload format. @@ -47,13 +56,39 @@ struct fscrypt_key { __u32 size; }; +/* + * New policy version with HKDF and key verification (recommended). + */ +#define FSCRYPT_POLICY_V2 2 +#define FSCRYPT_KEY_IDENTIFIER_SIZE 16 +struct fscrypt_policy_v2 { + __u8 version; + __u8 contents_encryption_mode; + __u8 filenames_encryption_mode; + __u8 flags; + __u8 __reserved[4]; + __u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; +}; + +/* Struct passed to FS_IOC_GET_ENCRYPTION_POLICY_EX */ +struct fscrypt_get_policy_ex_arg { + __u64 policy_size; /* input/output */ + union { + __u8 version; + struct fscrypt_policy_v1 v1; + struct fscrypt_policy_v2 v2; + } policy; /* output */ +}; + struct fscrypt_key_specifier { #define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR 1 +#define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER 2 __u32 type; __u32 __reserved; union { __u8 __reserved[32]; /* reserve some extra space */ __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + __u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; } u; }; @@ -88,6 +123,7 @@ struct fscrypt_get_key_status_arg { #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) #define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) #define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy) +#define FS_IOC_GET_ENCRYPTION_POLICY_EX _IOWR('f', 22, __u8[9]) /* size + version */ #define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg) #define FS_IOC_REMOVE_ENCRYPTION_KEY _IOW('f', 24, struct fscrypt_remove_key_arg) #define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 25, struct fscrypt_get_key_status_arg) From patchwork Tue Apr 2 15:45:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881937 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D992A15AC for ; Tue, 2 Apr 2019 15:48:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C837C201F5 for ; Tue, 2 Apr 2019 15:48:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BBAC1286A1; Tue, 2 Apr 2019 15:48:48 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 56C6D201F5 for ; Tue, 2 Apr 2019 15:48:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731461AbfDBPso (ORCPT ); Tue, 2 Apr 2019 11:48:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:37018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731289AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 72976208E4; Tue, 2 Apr 2019 15:48:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220116; bh=tcM0V4DW46qQuWBh2DXrd4oZAQjaLLpvpe8dO+k3HP4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R+LfqkZz5IoRJ1BQRhi9Jpeb0g5DwfmDx4xU0YUPxaGVIyonILE4j49tuPwgUg8MD iSgwXB0008DGN8nq0ixPLnq7m1WVWqeGkkNLQvvjWpog0WuIukEUjY8Sh1uf78Sdaj gixg4EUCb56SN+80WOTJBzyXWjWqKe0XGmG0oaHk= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 12/17] fscrypt: allow unprivileged users to add/remove keys for v2 policies Date: Tue, 2 Apr 2019 08:45:55 -0700 Message-Id: <20190402154600.32432-13-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Allow the FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY ioctls to be used by non-root users to add and remove encryption keys from the filesystem-level crypto keyrings, subject to limitations. Motivation: while privileged fscrypt key management is sufficient for some users (e.g. Android and Chromium OS, where a privileged process manages all keys), the old API by design also allows non-root users to set up and use encrypted directories, and we don't want to regress on that. Especially, we don't want to force users to continue using the old API, running into the visibility mismatch between files and keyrings and being unable to "lock" encrypted directories. Intuitively, the ioctls have to be privileged since they manipulate filesystem-level state. However, it's actually safe to make them unprivileged if we very carefully enforce some specific limitations. First, each key must be identified by a cryptographic hash so that a user can't add the wrong key for another user's files. For v2 encryption policies, we use the key_identifier for this. v1 policies don't have this, so managing keys for them remains privileged. Second, each key a user adds is charged to their quota for the keyrings service. Thus, a user can't exhaust memory by adding a huge number of keys. By default each non-root user is allowed up to 200 keys; this can be changed using the existing sysctl 'kernel.keys.maxkeys'. Third, if multiple users add the same key, we keep track of those users of the key (of which there remains a single copy), and won't really remove the key, i.e. "lock" the encrypted files, until all those users have removed it. This prevents denial of service attacks that would be possible under simpler schemes, such allowing the first user who added a key to remove it -- since that could be a malicious user who has compromised the key. Of course, encryption keys should be kept secret, but the idea is that using encryption should never be *less* secure than not using encryption, even if your key was compromised. We tolerate that a user will be unable to really remove a key, i.e. unable to "lock" their encrypted files, if another user has added the same key. But in a sense, this is actually a good thing because it will avoid providing a false notion of security where a key appears to have been removed when actually it's still in memory, available to any attacker who compromises the operating system kernel. Signed-off-by: Eric Biggers --- fs/crypto/fscrypt_private.h | 31 +++- fs/crypto/keyring.c | 310 +++++++++++++++++++++++++++++++++-- fs/crypto/keysetup.c | 18 +- include/uapi/linux/fscrypt.h | 9 +- 4 files changed, 340 insertions(+), 28 deletions(-) diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 9591f5fd72b33..5f679ba32cece 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -338,9 +338,16 @@ struct fscrypt_master_key { * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again. * - * Locking: protected by key->sem. + * Locking: protected by key->sem (outer) and mk_secret_sem (inner). + * The reason for two locks is that key->sem also protects modifying + * mk_users, which ranks it above the semaphore for the keyring key + * type, which is in turn above page faults (via keyring_read). But + * sometimes filesystems call fscrypt_get_encryption_info() from within + * a transaction, which ranks it below page faults. So we need a + * separate lock which protects mk_secret but not also mk_users. */ struct fscrypt_master_key_secret mk_secret; + struct rw_semaphore mk_secret_sem; /* * For v1 policy keys: an arbitrary key descriptor which was assigned by @@ -350,6 +357,22 @@ struct fscrypt_master_key { */ struct fscrypt_key_specifier mk_spec; + /* + * Keyring which contains a key of type 'key_type_fscrypt_user' for each + * user who has added this key. Normally each key will be added by just + * one user, but it's possible that multiple users share a key, and in + * that case we need to keep track of those users so that one user can't + * remove the key before the others want it removed too. + * + * This is NULL for v1 policy keys; those can only be added by root. + * + * Locking: in addition to this keyrings own semaphore, this is + * protected by the master key's key->sem, so we can do atomic + * search+insert. It can also be searched without taking any locks, but + * in that case the returned key may have already been removed. + */ + struct key *mk_users; + /* * Length of ->mk_decrypted_inodes, plus one if mk_secret is present. * Once this goes to 0, the master key is removed from ->s_master_keys. @@ -377,9 +400,9 @@ is_master_key_secret_present(const struct fscrypt_master_key_secret *secret) /* * The READ_ONCE() is only necessary for fscrypt_drop_inode() and * fscrypt_key_describe(). These run in atomic context, so they can't - * take key->sem and thus 'secret' can change concurrently which would - * be a data race. But they only need to know whether the secret *was* - * present at the time of check, so READ_ONCE() suffices. + * take ->mk_secret_sem and thus 'secret' can change concurrently which + * would be a data race. But they only need to know whether the secret + * *was* present at the time of check, so READ_ONCE() suffices. */ return READ_ONCE(secret->size) != 0; } diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index fe1b003975c4f..3d17c13136a4a 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -42,6 +42,7 @@ static void free_master_key(struct fscrypt_master_key *mk) for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++) crypto_free_skcipher(mk->mk_mode_keys[i]); + key_put(mk->mk_users); kzfree(mk); } @@ -101,7 +102,39 @@ static struct key_type key_type_fscrypt = { .describe = fscrypt_key_describe, }; -/* Search ->s_master_keys */ +static int fscrypt_user_key_instantiate(struct key *key, + struct key_preparsed_payload *prep) +{ + /* + * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for + * each key, regardless of the exact key size. The amount of memory + * actually used is greater than the size of the raw key anyway. + */ + return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE); +} + +static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m) +{ + seq_puts(m, key->description); +} + +/* + * Type of key in ->mk_users. Each key of this type represents a particular + * user who has added a particular master key. + * + * Note that the name of this key type really should be something like + * ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen + * mainly for simplicity of presentation in /proc/keys when read by a non-root + * user. And it is expected to be rare that a key is actually added by multiple + * users, since users should keep their encryption keys confidential. + */ +static struct key_type key_type_fscrypt_user = { + .name = ".fscrypt", + .instantiate = fscrypt_user_key_instantiate, + .describe = fscrypt_user_key_describe, +}; + +/* Search ->s_master_keys or ->mk_users */ static struct key *search_fscrypt_keyring(struct key *keyring, struct key_type *type, const char *description) @@ -127,6 +160,13 @@ static struct key *search_fscrypt_keyring(struct key *keyring, #define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1) +#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \ + (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \ + CONST_STRLEN("-users") + 1) + +#define FSCRYPT_MK_USER_DESCRIPTION_SIZE \ + (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1) + static void format_fs_keyring_description( char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], const struct super_block *sb) @@ -142,6 +182,23 @@ static void format_mk_description( master_key_spec_len(mk_spec), (u8 *)&mk_spec->u); } +static void format_mk_users_keyring_description( + char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE], + const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + sprintf(description, "fscrypt-%*phN-users", + FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier); +} + +static void format_mk_user_description( + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE], + const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + + sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE, + mk_identifier, __kuid_val(current_fsuid())); +} + /* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ static int allocate_filesystem_keyring(struct super_block *sb) { @@ -189,6 +246,81 @@ struct key *fscrypt_find_master_key(struct super_block *sb, return search_fscrypt_keyring(keyring, &key_type_fscrypt, description); } +static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE]; + struct key *keyring; + + format_mk_users_keyring_description(description, + mk->mk_spec.u.identifier); + keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, + current_cred(), KEY_POS_SEARCH | + KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); + + mk->mk_users = keyring; + return 0; +} + +/* + * Find the current user's key in the master key's ->mk_users. + * Returns ERR_PTR(-ENOKEY) if not found. + */ +static struct key *find_master_key_user(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; + + format_mk_user_description(description, mk->mk_spec.u.identifier); + return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user, + description); +} + +/* + * Give the current user a key in ->mk_users. This charges the user's quota and + * marks the master key as added by the current user, so that it cannot be + * removed by another user with the key. Either the master key's key->sem must + * be held for write, or the master key must be still undergoing initialization. + */ +static int add_master_key_user(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; + struct key *mk_user; + int err; + + format_mk_user_description(description, mk->mk_spec.u.identifier); + mk_user = key_alloc(&key_type_fscrypt_user, description, + current_fsuid(), current_gid(), current_cred(), + KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL); + if (IS_ERR(mk_user)) + return PTR_ERR(mk_user); + + err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL); + key_put(mk_user); + return err; +} + +/* + * Remove the current user's key from ->mk_users, if present. + * The master key's key->sem must be held for write. + */ +static int remove_master_key_user(struct fscrypt_master_key *mk) +{ + struct key *mk_user; + int err; + + mk_user = find_master_key_user(mk); + if (IS_ERR(mk_user)) { + if (mk_user != ERR_PTR(-ENOKEY)) + return PTR_ERR(mk_user); + return 0; + } + err = key_unlink(mk->mk_users, mk_user); + key_put(mk_user); + return err; +} + /* * Allocate a new fscrypt_master_key which contains the given secret, set it as * the payload of a new 'struct key' of type fscrypt, and link the 'struct key' @@ -210,11 +342,26 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret, mk->mk_spec = *mk_spec; move_master_key_secret(&mk->mk_secret, secret); + init_rwsem(&mk->mk_secret_sem); refcount_set(&mk->mk_refcount, 1); /* secret is present */ INIT_LIST_HEAD(&mk->mk_decrypted_inodes); spin_lock_init(&mk->mk_decrypted_inodes_lock); + if (mk_spec->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { + err = allocate_master_key_users_keyring(mk); + if (err) + goto out_free_mk; + err = add_master_key_user(mk); + if (err) + goto out_free_mk; + } + + /* + * Note that we don't charge this key to anyone's quota, since when + * ->mk_users is in use those keys are charged instead, and otherwise + * (when ->mk_users isn't in use) only root can add these keys. + */ format_mk_description(description, mk_spec); key = key_alloc(&key_type_fscrypt, description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), @@ -242,13 +389,45 @@ static int add_existing_master_key(struct fscrypt_master_key *mk, struct fscrypt_master_key_secret *secret, const struct fscrypt_key_specifier *mk_spec) { - if (is_master_key_secret_present(&mk->mk_secret)) - return 0; + struct key *mk_user; + bool rekey; + int err; + + /* + * If the current user is already in ->mk_users, then there's nothing to + * do. (Not applicable for v1 policy keys, which have NULL ->mk_users.) + */ + if (mk->mk_users) { + mk_user = find_master_key_user(mk); + if (mk_user != ERR_PTR(-ENOKEY)) { + if (IS_ERR(mk_user)) + return PTR_ERR(mk_user); + key_put(mk_user); + return 0; + } + } - if (!refcount_inc_not_zero(&mk->mk_refcount)) + /* If we'll be re-adding ->mk_secret, try to take the reference. */ + rekey = !is_master_key_secret_present(&mk->mk_secret); + if (rekey && !refcount_inc_not_zero(&mk->mk_refcount)) return KEY_DEAD; - move_master_key_secret(&mk->mk_secret, secret); + /* Add the current user to ->mk_users, if applicable. */ + if (mk->mk_users) { + err = add_master_key_user(mk); + if (err) { + if (rekey && refcount_dec_and_test(&mk->mk_refcount)) + return KEY_DEAD; + return err; + } + } + + /* Re-add the secret if needed. */ + if (rekey) { + down_write(&mk->mk_secret_sem); + move_master_key_secret(&mk->mk_secret, secret); + up_write(&mk->mk_secret_sem); + } return 0; } @@ -275,7 +454,7 @@ static int add_master_key(struct super_block *sb, } else { /* * Found the key in ->s_master_keys. Re-add the secret if - * needed. + * needed, and add the user to ->mk_users if needed. */ down_write(&key->sem); err = add_existing_master_key(key->payload.data[0], secret, @@ -297,6 +476,23 @@ static int add_master_key(struct super_block *sb, /* * Add a master encryption key to the filesystem, causing all files which were * encrypted with it to appear "unlocked" (decrypted) when accessed. + * + * When adding a key for use by v1 encryption policies, this ioctl is + * privileged, and userspace must provide the 'key_descriptor'. + * + * When adding a key for use by v2+ encryption policies, this ioctl is + * unprivileged. This is needed, in general, to allow non-root users to use + * encryption without encountering the visibility problems of process-subscribed + * keyrings and the inability to properly remove keys. This works by having + * each key identified by its cryptographically secure hash --- the + * 'key_identifier'. The cryptographic hash ensures that a malicious user + * cannot add the wrong key for a given identifier. Furthermore, each added key + * is charged to the appropriate user's quota for the keyrings service, which + * prevents a malicious user from adding too many keys. Finally, we forbid a + * user from removing a key while other users have added it too, which prevents + * a user who knows another user's key from causing a denial-of-service by + * removing it at an inopportune time. (We tolerate that a user who knows a key + * can prevent other users from removing it.) */ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) { @@ -325,11 +521,16 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) if (copy_from_user(secret.raw, uarg->raw, secret.size)) goto out_wipe_secret; - err = -EACCES; - if (!capable(CAP_SYS_ADMIN)) - goto out_wipe_secret; - - if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { + if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { + /* + * Only root can add keys that are identified by an arbitrary + * descriptor rather than by a cryptographic hash --- since + * otherwise a malicious user could add the wrong key. + */ + err = -EACCES; + if (!capable(CAP_SYS_ADMIN)) + goto out_wipe_secret; + } else { err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size); if (err) goto out_wipe_secret; @@ -481,10 +682,26 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg) if (!valid_key_spec(&arg.key_spec)) return -EINVAL; + if (arg.flags & ~FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS) + return -EINVAL; + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) return -EINVAL; - if (!capable(CAP_SYS_ADMIN)) + /* + * Only root can request that the key be removed no matter how many + * users have added it. + */ + if ((arg.flags & FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS) && + !capable(CAP_SYS_ADMIN)) + return -EACCES; + + /* + * Only root can add and remove keys that are identified by an arbitrary + * descriptor rather than by a cryptographic hash. + */ + if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR && + !capable(CAP_SYS_ADMIN)) return -EACCES; /* Find the key being removed. */ @@ -495,11 +712,35 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg) down_write(&key->sem); - /* Wipe the secret. */ + /* If relevant, remove current user's (or all users) usage of the key */ + if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) { + if (arg.flags & FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS) + err = keyring_clear(mk->mk_users); + else + err = remove_master_key_user(mk); + if (err) { + up_write(&key->sem); + goto out_put_key; + } + if (mk->mk_users->keys.nr_leaves_on_tree != 0) { + /* + * Other users have still added the key too. We removed + * the current user's usage of the key if there was one, + * but we still can't remove the key itself. + */ + err = -EUSERS; + up_write(&key->sem); + goto out_put_key; + } + } + + /* No usages remaining. Go ahead and wipe the secret. */ dead = false; if (is_master_key_secret_present(&mk->mk_secret)) { + down_write(&mk->mk_secret_sem); wipe_master_key_secret(&mk->mk_secret); dead = refcount_dec_and_test(&mk->mk_refcount); + up_write(&mk->mk_secret_sem); } up_write(&key->sem); if (dead) { @@ -513,6 +754,7 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg) /* Some inodes still reference this key; try to evict them. */ err = try_to_lock_encrypted_files(sb, mk); } +out_put_key: key_put(key); return err; } @@ -528,6 +770,15 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key); * of an encrypted directory without using a hack such as trying to open a * regular file in it (which can confuse the "incompletely removed" state with * absent or present). + * + * In addition, for v2 policy keys we allow applications to determine, via + * ->status_flags and ->user_count, whether the key has been added by the + * current user, by other users, or by both. Most applications should not need + * this, since ordinarily only one user should know a given key. However, if a + * secret key is shared by multiple users, applications may wish to add an + * already-present key to prevent other users from removing it. This ioctl can + * be used to check whether that really is the case before the work is done to + * add the key --- which might e.g. require prompting the user for a passphrase. */ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) { @@ -546,6 +797,8 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) return -EINVAL; + arg.status_flags = 0; + arg.user_count = 0; memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved)); key = fscrypt_find_master_key(sb, &arg.key_spec); @@ -566,6 +819,20 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) } arg.status = FSCRYPT_KEY_STATUS_PRESENT; + if (mk->mk_users) { + struct key *mk_user; + + arg.user_count = mk->mk_users->keys.nr_leaves_on_tree; + mk_user = find_master_key_user(mk); + if (!IS_ERR(mk_user)) { + arg.status_flags |= + FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF; + key_put(mk_user); + } else if (mk_user != ERR_PTR(-ENOKEY)) { + err = PTR_ERR(mk_user); + goto out_release_key; + } + } err = 0; out_release_key: up_read(&key->sem); @@ -579,10 +846,25 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status); int __init fscrypt_init_keyring(void) { - return register_key_type(&key_type_fscrypt); + int err; + + err = register_key_type(&key_type_fscrypt); + if (err) + return err; + + err = register_key_type(&key_type_fscrypt_user); + if (err) + goto err_unregister_fscrypt; + + return 0; + +err_unregister_fscrypt: + unregister_key_type(&key_type_fscrypt); + return err; } void fscrypt_exit_keyring(void) { unregister_key_type(&key_type_fscrypt); + unregister_key_type(&key_type_fscrypt_user); } diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index c81447a438ea9..6b6673355538c 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -283,10 +283,10 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, * * If the master key is found in the filesystem-level keyring, then the * corresponding 'struct key' is returned in *master_key_ret with - * ->sem read-locked. This is needed to ensure that only one task links the - * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create - * an fscrypt_info for the same inode), and to synchronize the key being removed - * with a new inode starting to use it. + * ->mk_secret_sem read-locked. This is needed to ensure that only one task + * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race + * to create an fscrypt_info for the same inode), and to synchronize the key + * being removed with a new inode starting to use it. */ static int setup_file_encryption_key(struct fscrypt_info *ci, struct key **master_key_ret) @@ -324,7 +324,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, } mk = key->payload.data[0]; - down_read(&key->sem); + down_read(&mk->mk_secret_sem); /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ if (!is_master_key_secret_present(&mk->mk_secret)) { @@ -358,7 +358,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci, return 0; out_release_key: - up_read(&key->sem); + up_read(&mk->mk_secret_sem); key_put(key); return err; } @@ -484,7 +484,9 @@ int fscrypt_get_encryption_info(struct inode *inode) res = 0; out: if (master_key) { - up_read(&master_key->sem); + struct fscrypt_master_key *mk = master_key->payload.data[0]; + + up_read(&mk->mk_secret_sem); key_put(master_key); } if (res == -ENOKEY) @@ -526,7 +528,7 @@ int fscrypt_drop_inode(struct inode *inode) mk = ci->ci_master_key->payload.data[0]; /* - * Note: since we aren't holding key->sem, the result here can + * Note: since we aren't holding ->mk_secret_sem, the result here can * immediately become outdated. But there's no correctness problem with * unnecessarily evicting. Nor is there a correctness problem with not * evicting while iput() is racing with the key being removed, since diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 26879e669dfa0..fd1c3e2b0b7c1 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -103,7 +103,9 @@ struct fscrypt_add_key_arg { /* Struct passed to FS_IOC_REMOVE_ENCRYPTION_KEY */ struct fscrypt_remove_key_arg { struct fscrypt_key_specifier key_spec; - __u32 __reserved[6]; +#define FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS 0x00000001 + __u32 flags; + __u32 __reserved[5]; }; /* Struct passed to FS_IOC_GET_ENCRYPTION_KEY_STATUS */ @@ -117,7 +119,10 @@ struct fscrypt_get_key_status_arg { #define FSCRYPT_KEY_STATUS_PRESENT 2 #define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED 3 __u32 status; - __u32 __out_reserved[15]; +#define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF 0x00000001 + __u32 status_flags; + __u32 user_count; + __u32 __out_reserved[13]; }; #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy) From patchwork Tue Apr 2 15:45:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881933 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1845215AC for ; Tue, 2 Apr 2019 15:48:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 08B792868C for ; Tue, 2 Apr 2019 15:48:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F1555287C8; Tue, 2 Apr 2019 15:48:46 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8F0C42868C for ; Tue, 2 Apr 2019 15:48:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730847AbfDBPsp (ORCPT ); Tue, 2 Apr 2019 11:48:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:36926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731323AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E6A492171F; Tue, 2 Apr 2019 15:48:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220117; bh=KmBDsI/LcwOa4M+22k/4vkcxnmCJ0qhjQzd+/krrPaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GsirEp018qvIrQseciOMD7LrbZGpdhwpWtaf46Ny4AnrJxvomreGOxsi3XFZO5ani d0gk1NZ+7as4xISRZXqEUO2J9U5Mcgw6cp0/bdYBWCHV6tzs+kb8gJJqPW8G4Htfue tOdwPNfBTIaMWa8MIQQiuGhiKUuqXkGA0Po2rCDM= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 13/17] fscrypt: require that key be added when setting a v2 encryption policy Date: Tue, 2 Apr 2019 08:45:56 -0700 Message-Id: <20190402154600.32432-14-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers By looking up the master keys in a filesystem-level keyring rather than in the calling processes' key hierarchy, it becomes possible for a user to set an encryption policy which refers to some key they don't actually know, then encrypt their files using that key. Cryptographically this isn't much of a problem, but the semantics of this would be a bit weird. Thus, enforce that a v2 encryption policy can only be set if the user has previously added the key, or has capable(CAP_FOWNER). We tolerate that this problem will continue to exist for v1 encryption policies, however; there is no way around that. Signed-off-by: Eric Biggers --- fs/crypto/fscrypt_private.h | 3 +++ fs/crypto/keyring.c | 47 +++++++++++++++++++++++++++++++++++++ fs/crypto/policy.c | 6 +++++ 3 files changed, 56 insertions(+) diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 5f679ba32cece..a398383ae9e34 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -411,6 +411,9 @@ extern struct key * fscrypt_find_master_key(struct super_block *sb, const struct fscrypt_key_specifier *mk_spec); +extern int fscrypt_verify_key_added(struct super_block *sb, + const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]); + extern int __init fscrypt_init_keyring(void); extern void fscrypt_exit_keyring(void); diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 3d17c13136a4a..2ccabf95f294c 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -562,6 +562,53 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) } EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key); +/* + * Verify that the current user has added a master key with the given identifier + * (returns -ENOKEY if not). This is needed to prevent a user from encrypting + * their files using some other user's key which they don't actually know. + * Cryptographically this isn't much of a problem, but the semantics of this + * would be a bit weird, so it's best to just forbid it. + * + * The system administrator (CAP_FOWNER) can override this, which should be + * enough for any use cases where encryption policies are being set using keys + * that were chosen ahead of time but aren't available at the moment. + * + * Note that the key may have already removed by the time this returns, but + * that's okay; we just care whether the key was there at some point. + * + * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code + */ +int fscrypt_verify_key_added(struct super_block *sb, + const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + struct fscrypt_key_specifier mk_spec; + struct key *key, *mk_user; + struct fscrypt_master_key *mk; + int err; + + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; + memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE); + + key = fscrypt_find_master_key(sb, &mk_spec); + if (IS_ERR(key)) { + err = PTR_ERR(key); + goto out; + } + mk = key->payload.data[0]; + mk_user = find_master_key_user(mk); + if (IS_ERR(mk_user)) { + err = PTR_ERR(mk_user); + } else { + key_put(mk_user); + err = 0; + } + key_put(key); +out: + if (err == -ENOKEY && capable(CAP_FOWNER)) + err = 0; + return err; +} + static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk) { struct fscrypt_info *ci; diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 912ff1d030796..fa86f96741308 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -209,6 +209,7 @@ static int set_encryption_policy(struct inode *inode, { union fscrypt_context ctx; int ctxsize; + int err; if (!fscrypt_supported_policy(policy)) return -EINVAL; @@ -227,6 +228,11 @@ static int set_encryption_policy(struct inode *inode, */ pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n", current->comm, current->pid); + } else { + err = fscrypt_verify_key_added(inode->i_sb, + policy->v2.master_key_identifier); + if (err) + return err; } ctxsize = fscrypt_new_context_from_policy(&ctx, policy); From patchwork Tue Apr 2 15:45:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881963 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 52A3A15AC for ; Tue, 2 Apr 2019 15:49:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 44235201F5 for ; Tue, 2 Apr 2019 15:49:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3825228691; Tue, 2 Apr 2019 15:49:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 66D94201F5 for ; Tue, 2 Apr 2019 15:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731540AbfDBPs7 (ORCPT ); Tue, 2 Apr 2019 11:48:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:36870 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731342AbfDBPsi (ORCPT ); Tue, 2 Apr 2019 11:48:38 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 65FDD21734; Tue, 2 Apr 2019 15:48:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220117; bh=No3yfIQYvQbNAxm366pcajxAnEE1z10+tSOuqrDVVDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HB+m6lb5CqeujWLWM1VctPE6ZFeTgRo/rvRqMycX1ptcjcSjzDalOMClAenIzekjm QCx4K32vl9C3tHTbjUzsFWZeO+CxjW8hB3frvhNSmP3275fNnvsCLL45HzOkS4qw7N o4aOr54sze2X8Gj7Z5/wvPWfZzTML4N8Lkhctp8I= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 14/17] ext4: wire up new fscrypt ioctls Date: Tue, 2 Apr 2019 08:45:57 -0700 Message-Id: <20190402154600.32432-15-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Wire up the new ioctls for adding and removing fscrypt keys to/from the filesystem, and the new ioctl for retrieving v2 encryption policies. FS_IOC_REMOVE_ENCRYPTION_KEY also required making ext4_drop_inode() call fscrypt_drop_inode(). For more details see Documentation/filesystems/fscrypt.rst, as well as the fscrypt patches that added the implementation of these ioctls. Signed-off-by: Eric Biggers --- fs/ext4/ioctl.c | 24 ++++++++++++++++++++++++ fs/ext4/super.c | 3 +++ 2 files changed, 27 insertions(+) diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index bab3da4f1e0d3..3ed66628e9301 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1074,6 +1074,26 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) case EXT4_IOC_GET_ENCRYPTION_POLICY: return fscrypt_ioctl_get_policy(filp, (void __user *)arg); + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + if (!ext4_has_feature_encrypt(sb)) + return -EOPNOTSUPP; + return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg); + + case FS_IOC_ADD_ENCRYPTION_KEY: + if (!ext4_has_feature_encrypt(sb)) + return -EOPNOTSUPP; + return fscrypt_ioctl_add_key(filp, (void __user *)arg); + + case FS_IOC_REMOVE_ENCRYPTION_KEY: + if (!ext4_has_feature_encrypt(sb)) + return -EOPNOTSUPP; + return fscrypt_ioctl_remove_key(filp, (const void __user *)arg); + + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: + if (!ext4_has_feature_encrypt(sb)) + return -EOPNOTSUPP; + return fscrypt_ioctl_get_key_status(filp, (void __user *)arg); + case EXT4_IOC_FSGETXATTR: { struct fsxattr fa; @@ -1192,6 +1212,10 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case EXT4_IOC_SET_ENCRYPTION_POLICY: case EXT4_IOC_GET_ENCRYPTION_PWSALT: case EXT4_IOC_GET_ENCRYPTION_POLICY: + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + case FS_IOC_ADD_ENCRYPTION_KEY: + case FS_IOC_REMOVE_ENCRYPTION_KEY: + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: case EXT4_IOC_SHUTDOWN: case FS_IOC_GETFSMAP: break; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 6ed4eb81e6743..624543a3f4d3e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1103,6 +1103,9 @@ static int ext4_drop_inode(struct inode *inode) { int drop = generic_drop_inode(inode); + if (!drop) + drop = fscrypt_drop_inode(inode); + trace_ext4_drop_inode(inode, drop); return drop; } From patchwork Tue Apr 2 15:45:58 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881923 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A453015AC for ; Tue, 2 Apr 2019 15:48:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8FCBD201F5 for ; Tue, 2 Apr 2019 15:48:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 84599286A1; Tue, 2 Apr 2019 15:48:42 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 22932201F5 for ; Tue, 2 Apr 2019 15:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731427AbfDBPsk (ORCPT ); Tue, 2 Apr 2019 11:48:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:37136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731383AbfDBPsj (ORCPT ); Tue, 2 Apr 2019 11:48:39 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D789321741; Tue, 2 Apr 2019 15:48:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220118; bh=sXTzCdkJrYXxv/SHdPjmdIL5PN0MRwSnIQ9nL31vSRk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ganR7fpq8u+FfoCR+Ev16F1/7Te9U+qa4UwB7Hu9reApO8UOxEaElRGkAex1tkmqp wyH4sEp0exKkh0p2Qe/uAa88fMSTWm8n0ERqHpymeftJDZLQWi8Q3cLeAUpyo9T9Jc EMuq1Ps8/0cB4CHthASEFkp7JlIc56eHoG4mM5BU= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 15/17] f2fs: wire up new fscrypt ioctls Date: Tue, 2 Apr 2019 08:45:58 -0700 Message-Id: <20190402154600.32432-16-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Wire up the new ioctls for adding and removing fscrypt keys to/from the filesystem, and the new ioctl for retrieving v2 encryption policies. FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call fscrypt_drop_inode(). For more details see Documentation/filesystems/fscrypt.rst, as well as the fscrypt patches that added the implementation of these ioctls. Signed-off-by: Eric Biggers --- fs/f2fs/file.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ fs/f2fs/super.c | 2 ++ 2 files changed, 48 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 5742ab8b57dc6..251e374353da8 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2095,6 +2095,40 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg) return err; } +static int f2fs_ioc_get_encryption_policy_ex(struct file *filp, + unsigned long arg) +{ + if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg); +} + +static int f2fs_ioc_add_encryption_key(struct file *filp, unsigned long arg) +{ + if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fscrypt_ioctl_add_key(filp, (void __user *)arg); +} + +static int f2fs_ioc_remove_encryption_key(struct file *filp, unsigned long arg) +{ + if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fscrypt_ioctl_remove_key(filp, (const void __user *)arg); +} + +static int f2fs_ioc_get_encryption_key_status(struct file *filp, + unsigned long arg) +{ + if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp)))) + return -EOPNOTSUPP; + + return fscrypt_ioctl_get_key_status(filp, (void __user *)arg); +} + static int f2fs_ioc_gc(struct file *filp, unsigned long arg) { struct inode *inode = file_inode(filp); @@ -3000,6 +3034,14 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return f2fs_ioc_get_encryption_policy(filp, arg); case F2FS_IOC_GET_ENCRYPTION_PWSALT: return f2fs_ioc_get_encryption_pwsalt(filp, arg); + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + return f2fs_ioc_get_encryption_policy_ex(filp, arg); + case FS_IOC_ADD_ENCRYPTION_KEY: + return f2fs_ioc_add_encryption_key(filp, arg); + case FS_IOC_REMOVE_ENCRYPTION_KEY: + return f2fs_ioc_remove_encryption_key(filp, arg); + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: + return f2fs_ioc_get_encryption_key_status(filp, arg); case F2FS_IOC_GARBAGE_COLLECT: return f2fs_ioc_gc(filp, arg); case F2FS_IOC_GARBAGE_COLLECT_RANGE: @@ -3119,6 +3161,10 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case F2FS_IOC_SET_ENCRYPTION_POLICY: case F2FS_IOC_GET_ENCRYPTION_PWSALT: case F2FS_IOC_GET_ENCRYPTION_POLICY: + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + case FS_IOC_ADD_ENCRYPTION_KEY: + case FS_IOC_REMOVE_ENCRYPTION_KEY: + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: case F2FS_IOC_GARBAGE_COLLECT: case F2FS_IOC_GARBAGE_COLLECT_RANGE: case F2FS_IOC_WRITE_CHECKPOINT: diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index f2aaa2cc6b3e0..7219b3b2af759 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -934,6 +934,8 @@ static int f2fs_drop_inode(struct inode *inode) return 0; } ret = generic_drop_inode(inode); + if (!ret) + ret = fscrypt_drop_inode(inode); trace_f2fs_drop_inode(inode, ret); return ret; } From patchwork Tue Apr 2 15:45:59 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881945 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 517F115AC for ; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3C84A201F5 for ; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 31152286A1; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C93E7201F5 for ; Tue, 2 Apr 2019 15:48:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731511AbfDBPsu (ORCPT ); Tue, 2 Apr 2019 11:48:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:37158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729212AbfDBPsk (ORCPT ); Tue, 2 Apr 2019 11:48:40 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 57EBA20857; Tue, 2 Apr 2019 15:48:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220118; bh=41GP8Yjo0+8dQSPM4iw7HW6C6zzvGO0pLKV+NuTF9s8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YG7XC8W9V997ZoH5DN6+mEANCrE0ICM8BzrXRiftyUfaEYHTpqmHCg2TTaerajB4d TrEJVbR2xA4A8P6/6D7xyersephTYeaYVy52+hweySesJNHY/7hzRMM4ZBW3x8u2rp 9ogcy218bkDv9lQPpMjRgpW7h7O7J8Yb9lhU3epA= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 16/17] ubifs: wire up new fscrypt ioctls Date: Tue, 2 Apr 2019 08:45:59 -0700 Message-Id: <20190402154600.32432-17-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Wire up the new ioctls for adding and removing fscrypt keys to/from the filesystem, and the new ioctl for retrieving v2 encryption policies. FS_IOC_REMOVE_ENCRYPTION_KEY also required making UBIFS use fscrypt_drop_inode(). For more details see Documentation/filesystems/fscrypt.rst, as well as the fscrypt patches that added the implementation of these ioctls. Signed-off-by: Eric Biggers --- fs/ubifs/ioctl.c | 23 +++++++++++++++++------ fs/ubifs/super.c | 11 +++++++++++ 2 files changed, 28 insertions(+), 6 deletions(-) diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c index 82e4e6a30b044..3c640a7e937f4 100644 --- a/fs/ubifs/ioctl.c +++ b/fs/ubifs/ioctl.c @@ -205,13 +205,20 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg) return -EOPNOTSUPP; #endif } - case FS_IOC_GET_ENCRYPTION_POLICY: { -#ifdef CONFIG_FS_ENCRYPTION + case FS_IOC_GET_ENCRYPTION_POLICY: return fscrypt_ioctl_get_policy(file, (void __user *)arg); -#else - return -EOPNOTSUPP; -#endif - } + + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + return fscrypt_ioctl_get_policy_ex(file, (void __user *)arg); + + case FS_IOC_ADD_ENCRYPTION_KEY: + return fscrypt_ioctl_add_key(file, (void __user *)arg); + + case FS_IOC_REMOVE_ENCRYPTION_KEY: + return fscrypt_ioctl_remove_key(file, (const void __user *)arg); + + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: + return fscrypt_ioctl_get_key_status(file, (void __user *)arg); default: return -ENOTTY; @@ -230,6 +237,10 @@ long ubifs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) break; case FS_IOC_SET_ENCRYPTION_POLICY: case FS_IOC_GET_ENCRYPTION_POLICY: + case FS_IOC_GET_ENCRYPTION_POLICY_EX: + case FS_IOC_ADD_ENCRYPTION_KEY: + case FS_IOC_REMOVE_ENCRYPTION_KEY: + case FS_IOC_GET_ENCRYPTION_KEY_STATUS: break; default: return -ENOIOCTLCMD; diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c index 8dc2818fdd849..cd4a3e2be2043 100644 --- a/fs/ubifs/super.c +++ b/fs/ubifs/super.c @@ -334,6 +334,16 @@ static int ubifs_write_inode(struct inode *inode, struct writeback_control *wbc) return err; } +static int ubifs_drop_inode(struct inode *inode) +{ + int drop = generic_drop_inode(inode); + + if (!drop) + drop = fscrypt_drop_inode(inode); + + return drop; +} + static void ubifs_evict_inode(struct inode *inode) { int err; @@ -1982,6 +1992,7 @@ const struct super_operations ubifs_super_operations = { .destroy_inode = ubifs_destroy_inode, .put_super = ubifs_put_super, .write_inode = ubifs_write_inode, + .drop_inode = ubifs_drop_inode, .evict_inode = ubifs_evict_inode, .statfs = ubifs_statfs, .dirty_inode = ubifs_dirty_inode, From patchwork Tue Apr 2 15:46:00 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 10881947 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D463E13B5 for ; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C1DD32868C for ; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B640D286A1; Tue, 2 Apr 2019 15:48:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9FBEB2868C for ; Tue, 2 Apr 2019 15:48:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731252AbfDBPsv (ORCPT ); Tue, 2 Apr 2019 11:48:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:37006 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730682AbfDBPsl (ORCPT ); Tue, 2 Apr 2019 11:48:41 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CB97C21738; Tue, 2 Apr 2019 15:48:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554220119; bh=VU15faQWCEDPlU1a3eVIq9fNhmdp0HrzJYVL077CcEA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DaSVWFSNTJtDACT5yNAa9a6KsFmgwQ6XG4krYEHansHB4mRNy1KCM0IbJPvAfWH/s NbXi1PYrnqcBPOe+GtO/zea1CqBMlbEo5/f47weDLmhpvt4NCTniUC76So5wyp1GUE mxMA3iaxT/ZRrdMUONcC7jY0MPv3VfzVKwDVt2SI= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala Subject: [PATCH v4 17/17] fscrypt: document the new ioctls and policy version Date: Tue, 2 Apr 2019 08:46:00 -0700 Message-Id: <20190402154600.32432-18-ebiggers@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190402154600.32432-1-ebiggers@kernel.org> References: <20190402154600.32432-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Update the fscrypt documentation file to catch up to all the latest changes, including the new ioctls to manage master encryption keys in the filesystem-level keyring and the support for v2 encryption policies. Signed-off-by: Eric Biggers --- Documentation/filesystems/fscrypt.rst | 648 +++++++++++++++++++++----- 1 file changed, 532 insertions(+), 116 deletions(-) diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 4f9df6ba669e5..c480bd4d9a47c 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -72,6 +72,9 @@ Online attacks fscrypt (and storage encryption in general) can only provide limited protection, if any at all, against online attacks. In detail: +Side-channel attacks +~~~~~~~~~~~~~~~~~~~~ + fscrypt is only resistant to side-channel attacks, such as timing or electromagnetic attacks, to the extent that the underlying Linux Cryptographic API algorithms are. If a vulnerable algorithm is used, @@ -80,29 +83,84 @@ attacker to mount a side channel attack against the online system. Side channel attacks may also be mounted against applications consuming decrypted data. -After an encryption key has been provided, fscrypt is not designed to -hide the plaintext file contents or filenames from other users on the -same system, regardless of the visibility of the keyring key. -Instead, existing access control mechanisms such as file mode bits, -POSIX ACLs, LSMs, or mount namespaces should be used for this purpose. -Also note that as long as the encryption keys are *anywhere* in -memory, an online attacker can necessarily compromise them by mounting -a physical attack or by exploiting any kernel security vulnerability -which provides an arbitrary memory read primitive. - -While it is ostensibly possible to "evict" keys from the system, -recently accessed encrypted files will remain accessible at least -until the filesystem is unmounted or the VFS caches are dropped, e.g. -using ``echo 2 > /proc/sys/vm/drop_caches``. Even after that, if the -RAM is compromised before being powered off, it will likely still be -possible to recover portions of the plaintext file contents, if not -some of the encryption keys as well. (Since Linux v4.12, all -in-kernel keys related to fscrypt are sanitized before being freed. -However, userspace would need to do its part as well.) - -Currently, fscrypt does not prevent a user from maliciously providing -an incorrect key for another user's existing encrypted files. A -protection against this is planned. +Unauthorized file access +~~~~~~~~~~~~~~~~~~~~~~~~ + +After an encryption key has been added, fscrypt does not hide the +plaintext file contents or filenames from other users on the same +system. Instead, existing access control mechanisms such as file mode +bits, POSIX ACLs, LSMs, or namespaces should be used for this purpose. + +(For the reasoning behind this, understand that while the key is +added, the confidentiality of the data, from the perspective of the +system itself, is *not* protected by the mathematical properties of +encryption but rather only by the correctness of the kernel. +Therefore, any encryption-specific access control checks would merely +be enforced by kernel *code* and therefore would be largely redundant +with the wide variety of access control mechanisms already available.) + +Kernel memory compromise +~~~~~~~~~~~~~~~~~~~~~~~~ + +An attacker who compromises the system enough to read from arbitrary +memory, e.g. by mounting a physical attack or by exploiting a kernel +security vulnerability, can compromise all encryption keys that are +currently in use. + +However, fscrypt allows encryption keys to be removed from the kernel, +which may protect them from later compromise. + +In more detail, the FS_IOC_REMOVE_ENCRYPTION_KEY ioctl will wipe a +master encryption key from kernel memory. Moreover, it will try to +evict all cached inodes which had been "unlocked" using the key, +thereby wiping their per-file keys and making them once again appear +"locked", i.e. in ciphertext or encrypted form. + +However, FS_IOC_REMOVE_ENCRYPTION_KEY has some limitations: + +- Per-file keys for in-use files will *not* be removed or wiped. + Therefore, for maximum effect, userspace should close the relevant + encrypted files and directories before removing a master key, as + well as kill any processes whose working directory is in an affected + encrypted directory. + +- The kernel cannot magically wipe copies of the master key(s) that + userspace might have as well. Therefore, userspace must wipe all + copies of the master key(s) it makes as well. Naturally, the same + also applies to all higher levels in the key hierarchy. Userspace + should also follow other security precautions such as mlock()ing + memory containing keys to prevent it from being swapped out. + +- In general, decrypted contents and filenames in the kernel VFS + caches are freed but not wiped. Therefore, portions thereof may be + recoverable from freed memory, even after the corresponding key(s) + were wiped. To partially solve this, you can set + CONFIG_PAGE_POISONING=y in your kernel config and add page_poison=1 + to your kernel command line. However, this has a performance cost. + +- Secret keys might still exist in CPU registers, in crypto + accelerator hardware (if used by the crypto API to implement any of + the algorithms), or in other places not explicitly considered here. + +Limitations of v1 policies +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +v1 encryption policies have some weaknesses with respect to online +attacks: + +- There is no verification that the provided master key is correct. + Consequently, malicious users can associate the wrong key with + encrypted files, even files to which they have only read-only + access. + +- A compromise of a per-file key also compromises the master key from + which it was derived. + +- Non-root users cannot securely remove encryption keys. + +All the above problems are fixed with v2 encryption policies. For +this reason among others, it is recommended to use v2 encryption +policies on all new encrypted directories. Key hierarchy ============= @@ -123,11 +181,46 @@ appropriate master key. There can be any number of master keys, each of which protects any number of directory trees on any number of filesystems. -Userspace should generate master keys either using a cryptographically -secure random number generator, or by using a KDF (Key Derivation -Function). Note that whenever a KDF is used to "stretch" a -lower-entropy secret such as a passphrase, it is critical that a KDF -designed for this purpose be used, such as scrypt, PBKDF2, or Argon2. +Master keys should be pseudorandom, i.e. indistinguishable from random +bytestrings of the same length. This implies that users **must not** +directly use a password as a master key, zero-pad a shorter key, or +repeat a shorter key. Instead, users should generate master keys +either using a cryptographically secure random number generator, or by +using a KDF (Key Derivation Function). Note that whenever a KDF is +used to "stretch" a lower-entropy secret such as a passphrase, it is +critical that a KDF designed for this purpose be used, such as scrypt, +PBKDF2, or Argon2. + +Key derivation function +----------------------- + +With one exception, fscrypt never uses the master key(s) for +encryption directly. Instead, they are only used as input to a KDF +(Key Derivation Function) to derive the actual keys. + +The KDF used for a particular master key differs depending on whether +the key is used for v1 encryption policies or for v2 encryption +policies. Users **must not** use the same key for both v1 and v2 +encryption policies. + +For v1 encryption policies, the KDF only supports deriving per-file +encryption keys. It works by encrypting the master key with +AES-128-ECB, using the file's 16-byte nonce as the AES key. The +resulting ciphertext is used as the derived key. If the ciphertext is +longer than needed, then it is truncated to the needed length. + +For v2 encryption policies, the KDF is HKDF-SHA512. The master key is +passed as the "input keying material", a fixed value is passed as the +"salt", and a distinct "application-specific information string" is +used for each distinct key to be derived. For example, when a +per-file encryption key is derived, the application-specific +information string is the file's nonce prefixed with a context byte. +Different context bytes are used for other types of derived keys. + +HKDF-SHA512 is preferred to the original AES-128-ECB based KDF because +HKDF is more flexible, is nonreversible, and evenly distributes +entropy from the master key. HKDF is also standardized and widely +used by other software, whereas the AES-128-ECB based KDF is ad-hoc. Per-file keys ------------- @@ -138,29 +231,9 @@ files doesn't map to the same ciphertext, or vice versa. In most cases, fscrypt does this by deriving per-file keys. When a new encrypted inode (regular file, directory, or symlink) is created, fscrypt randomly generates a 16-byte nonce and stores it in the -inode's encryption xattr. Then, it uses a KDF (Key Derivation -Function) to derive the file's key from the master key and nonce. - -The Adiantum encryption mode (see `Encryption modes and usage`_) is -special, since it accepts longer IVs and is suitable for both contents -and filenames encryption. For it, a "direct key" option is offered -where the file's nonce is included in the IVs and the master key is -used for encryption directly. This improves performance; however, -users must not use the same master key for any other encryption mode. - -Below, the KDF and design considerations are described in more detail. - -The current KDF works by encrypting the master key with AES-128-ECB, -using the file's nonce as the AES key. The output is used as the -derived key. If the output is longer than needed, then it is -truncated to the needed length. - -Note: this KDF meets the primary security requirement, which is to -produce unique derived keys that preserve the entropy of the master -key, assuming that the master key is already a good pseudorandom key. -However, it is nonstandard and has some problems such as being -reversible, so it is generally considered to be a mistake! It may be -replaced with HKDF or another more standard KDF in the future. +inode's encryption xattr. Then, it uses a KDF (as described in `Key +derivation function`_) to derive the file's key from the master key +and nonce. Key derivation was chosen over key wrapping because wrapped keys would require larger xattrs which would be less likely to fit in-line in the @@ -176,6 +249,37 @@ rejected as it would have prevented ext4 filesystems from being resized, and by itself still wouldn't have been sufficient to prevent the same key from being directly reused for both XTS and CTS-CBC. +DIRECT_KEY and per-mode keys +---------------------------- + +The Adiantum encryption mode (see `Encryption modes and usage`_) is +suitable for both contents and filenames encryption, and it accepts +long IVs --- long enough to hold both an 8-byte logical block number +and a 16-byte per-file nonce. Also, the overhead of each Adiantum key +is greater than that of an AES-256-XTS key. + +Therefore, to improve performance and save memory, for Adiantum a +"direct key" configuration is supported. When the user has enabled +this by setting FSCRYPT_POLICY_FLAG_DIRECT_KEY in the fscrypt policy, +per-file keys are not used. Instead, whenever any data (contents or +filenames) is encrypted, the file's 16-byte nonce is included in the +IV. Moreover: + +- For v1 encryption policies, the encryption is done directly with the + master key. Because of this, users **must not** use the same master + key for any other purpose, even for other v1 policies. + +- For v2 encryption policies, the encryption is done with a per-mode + key derived using the KDF. Users may use the same master key for + other v2 encryption policies. + +Key identifiers +--------------- + +For master keys used for v2 encryption policies, a unique 16-byte "key +identifier" is also derived using the KDF. This value is stored in +the clear, since it is needed to reliably identify the key itself. + Encryption modes and usage ========================== @@ -271,21 +375,38 @@ Setting an encryption policy The FS_IOC_SET_ENCRYPTION_POLICY ioctl sets an encryption policy on an empty directory or verifies that a directory or regular file already has the specified encryption policy. It takes in a pointer to a -:c:type:`struct fscrypt_policy`, defined as follows:: +:c:type:`struct fscrypt_policy_v1` or a :c:type:`struct +fscrypt_policy_v2`, defined as follows:: - #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 - - struct fscrypt_policy { + #define FSCRYPT_POLICY_V1 0 + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 + struct fscrypt_policy_v1 { __u8 version; __u8 contents_encryption_mode; __u8 filenames_encryption_mode; __u8 flags; __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; }; + #define fscrypt_policy fscrypt_policy_v1 + + #define FSCRYPT_POLICY_V2 2 + #define FSCRYPT_KEY_IDENTIFIER_SIZE 16 + struct fscrypt_policy_v2 { + __u8 version; + __u8 contents_encryption_mode; + __u8 filenames_encryption_mode; + __u8 flags; + __u8 __reserved[4]; + __u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + }; This structure must be initialized as follows: -- ``version`` must be 0. +- ``version`` must be FSCRYPT_POLICY_V1 (0) if the struct is + :c:type:`fscrypt_policy_v1` or FSCRYPT_POLICY_V2 (2) if the struct + is :c:type:`fscrypt_policy_v2`. (Note: we refer to the original + policy version as "v1", though its version code is really 0.) For + new encrypted directories, use v2 policies. - ``contents_encryption_mode`` and ``filenames_encryption_mode`` must be set to constants from ```` which identify the @@ -295,21 +416,30 @@ This structure must be initialized as follows: - ``flags`` must contain a value from ```` which identifies the amount of NUL-padding to use when encrypting - filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3). In - addition, if the chosen encryption modes are both + filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3). + Additionally, if the encryption modes are both FSCRYPT_MODE_ADIANTUM, this can contain - FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should - be used directly, without key derivation. + FSCRYPT_POLICY_FLAG_DIRECT_KEY; see `DIRECT_KEY and per-mode keys`_. -- ``master_key_descriptor`` specifies how to find the master key in - the keyring; see `Adding keys`_. It is up to userspace to choose a - unique ``master_key_descriptor`` for each master key. The e4crypt - and fscrypt tools use the first 8 bytes of +- For v2 encryption policies, ``__reserved`` must be zeroed. + +- For v1 encryption policies, ``master_key_descriptor`` specifies how + to find the master key in a keyring; see `Adding keys`_. It is up + to userspace to choose a unique ``master_key_descriptor`` for each + master key. The e4crypt and fscrypt tools use the first 8 bytes of ``SHA-512(SHA-512(master_key))``, but this particular scheme is not required. Also, the master key need not be in the keyring yet when FS_IOC_SET_ENCRYPTION_POLICY is executed. However, it must be added before any files can be created in the encrypted directory. + For v2 encryption policies, ``master_key_descriptor`` has been + replaced with ``master_key_identifier``, which is longer and cannot + be arbitrarily chosen. Instead, the key must first be added using + FS_IOC_ADD_ENCRYPTION_KEY, as described in `Adding keys`_. Then, + the ``key_spec.u.identifier`` the kernel returned in the + :c:type:`struct fscrypt_add_key_arg` must be used as the + ``master_key_identifier`` in the :c:type:`struct fscrypt_policy_v2`. + If the file is not yet encrypted, then FS_IOC_SET_ENCRYPTION_POLICY verifies that the file is an empty directory. If so, the specified encryption policy is assigned to the directory, turning it into an @@ -325,6 +455,15 @@ policy exactly matches the actual one. If they match, then the ioctl returns 0. Otherwise, it fails with EEXIST. This works on both regular files and directories, including nonempty directories. +When a v2 encryption policy is assigned to a directory, it is also +required that either the specified key has been added by the current +user or that the caller has CAP_FOWNER in the initial user namespace. +(This is needed to prevent a user from encrypting their data with +another user's key.) The key must remain added while +FS_IOC_SET_ENCRYPTION_POLICY is executing. However, if the new +encrypted directory does not need to be accessed immediately, then the +key can be removed right away afterwards. + Note that the ext4 filesystem does not allow the root directory to be encrypted, even if it is empty. Users who want to encrypt an entire filesystem with one key should consider using dm-crypt instead. @@ -337,7 +476,11 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors: - ``EEXIST``: the file is already encrypted with an encryption policy different from the one specified - ``EINVAL``: an invalid encryption policy was specified (invalid - version, mode(s), or flags) + version, mode(s), or flags; or reserved bits were set) +- ``ENOKEY``: a v2 encryption policy was specified, but the key with + the specified ``master_key_identifier`` has not been added, nor does + the process have the CAP_FOWNER capability in the initial user + namespace - ``ENOTDIR``: the file is unencrypted and is a regular file, not a directory - ``ENOTEMPTY``: the file is unencrypted and is a nonempty directory @@ -356,25 +499,78 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors: Getting an encryption policy ---------------------------- -The FS_IOC_GET_ENCRYPTION_POLICY ioctl retrieves the :c:type:`struct -fscrypt_policy`, if any, for a directory or regular file. See above -for the struct definition. No additional permissions are required -beyond the ability to open the file. +Two ioctls are available to get a file's encryption policy: + +- FS_IOC_GET_ENCRYPTION_POLICY_EX +- FS_IOC_GET_ENCRYPTION_POLICY + +The extended (_EX) version of the ioctl is more general and is +recommended to use when possible. However, on older kernels only the +original ioctl is available. Applications should try the extended +version, and if it fails with ENOTTY fall back to the original +version. + +Preferred method +~~~~~~~~~~~~~~~~ + +The FS_IOC_GET_ENCRYPTION_POLICY_EX ioctl retrieves the encryption +policy, if any, for a directory or regular file. No additional +permissions are required beyond the ability to open the file. It +takes in a pointer to a :c:type:`struct fscrypt_get_policy_ex_arg`, +defined as follows:: + + struct fscrypt_get_policy_ex_arg { + __u64 policy_size; /* input/output */ + union { + __u8 version; + struct fscrypt_policy_v1 v1; + struct fscrypt_policy_v2 v2; + } policy; /* output */ + }; + +The caller must initialize ``policy_size`` to the size available for +the policy struct, i.e. ``sizeof(arg.policy)``. + +On success, the policy struct is returned in ``policy``, and its +actual size is returned in ``policy_size``. ``policy.version`` should +be checked to determine the version of policy returned. Note that the +version code for the "v1" policy is actually 0 (FSCRYPT_POLICY_V1). -FS_IOC_GET_ENCRYPTION_POLICY can fail with the following errors: +FS_IOC_GET_ENCRYPTION_POLICY_EX can fail with the following errors: - ``EINVAL``: the file is encrypted, but it uses an unrecognized - encryption context format + encryption policy version - ``ENODATA``: the file is not encrypted -- ``ENOTTY``: this type of filesystem does not implement encryption +- ``ENOTTY``: this type of filesystem does not implement encryption, + or this kernel is too old to support FS_IOC_GET_ENCRYPTION_POLICY_EX + (try FS_IOC_GET_ENCRYPTION_POLICY instead) - ``EOPNOTSUPP``: the kernel was not configured with encryption support for this filesystem +- ``EOVERFLOW``: the file is encrypted and uses a recognized + encryption policy version, but the policy struct does not fit into + the provided buffer Note: if you only need to know whether a file is encrypted or not, on most filesystems it is also possible to use the FS_IOC_GETFLAGS ioctl and check for FS_ENCRYPT_FL, or to use the statx() system call and check for STATX_ATTR_ENCRYPTED in stx_attributes. +Legacy method +~~~~~~~~~~~~~ + +The FS_IOC_GET_ENCRYPTION_POLICY ioctl can also retrieve the +encryption policy, if any, for a directory or regular file. However, +unlike the extended version (FS_IOC_GET_ENCRYPTION_POLICY_EX), +FS_IOC_GET_ENCRYPTION_POLICY only supports the original policy +version. It takes in a pointer directly to a :c:type:`struct +fscrypt_policy_v1` rather than a :c:type:`struct +fscrypt_get_policy_ex_arg`. + +The error codes for FS_IOC_GET_ENCRYPTION_POLICY are the same as those +for FS_IOC_GET_ENCRYPTION_POLICY_EX, except that +FS_IOC_GET_ENCRYPTION_POLICY also returns ``EINVAL`` if the file is +encrypted using a newer encryption policy version. + Getting the per-filesystem salt ------------------------------- @@ -390,8 +586,98 @@ generate and manage any needed salt(s) in userspace. Adding keys ----------- -To provide a master key, userspace must add it to an appropriate -keyring using the add_key() system call (see: +Preferred method +~~~~~~~~~~~~~~~~ + +The FS_IOC_ADD_ENCRYPTION_KEY ioctl adds a master encryption key to +the filesystem, making all files on the filesystem which were +encrypted using that key appear "unlocked", i.e. in plaintext form. +It can be executed on any file or directory on the target filesystem, +but using the filesystem's root directory is recommended. It takes in +a pointer to a :c:type:`struct fscrypt_add_key_arg`, defined as +follows:: + + struct fscrypt_add_key_arg { + struct fscrypt_key_specifier key_spec; + __u32 raw_size; + __u32 __reserved[9]; + __u8 raw[]; + }; + + struct fscrypt_key_specifier { + #define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR 1 + #define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER 2 + __u32 type; + __u32 __reserved; + union { + __u8 __reserved[32]; /* reserve some extra space */ + __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + __u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + } u; + }; + +:c:type:`struct fscrypt_add_key_arg` must be zeroed, then initialized +as follows: + +- If the key is being added for use by v1 encryption policies, then + ``key_spec.type`` must contain FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR, and + ``key_spec.u.descriptor`` must contain the descriptor of the key + being added, corresponding to the value in the + ``master_key_descriptor`` field of :c:type:`struct + fscrypt_policy_v1`. To add this type of key, the calling process + must have the CAP_SYS_ADMIN capability in the initial user + namespace. + + Alternatively, if the key is being added for use by v2 encryption + policies, then ``key_spec.type`` must contain + FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER, and ``key_spec.u.identifier`` is + an *output* field which the kernel fills in with a cryptographic + hash of the key. To add this type of key, the calling process does + not need any privileges. However, the number of keys that can be + added is limited by the user's quota for the keyrings service (see + ``Documentation/security/keys/core.rst``). + +- ``raw_size`` must be the size of the ``raw`` key provided, in bytes. + +- ``raw`` is a variable-length field which must contain the actual + key, ``raw_size`` bytes long. + +FS_IOC_ADD_ENCRYPTION_KEY can fail with the following errors: + +- ``EACCES``: FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR was specified, but the + caller does not have the CAP_SYS_ADMIN capability in the initial + user namespace +- ``EDQUOT``: the key quota for this user would be exceeded by adding + the key +- ``EINVAL``: invalid key size or key specifier type, or reserved bits + were set +- ``ENOTTY``: this type of filesystem does not implement encryption +- ``EOPNOTSUPP``: the kernel was not configured with encryption + support for this filesystem, or the filesystem superblock has not + had encryption enabled on it + +Legacy method +~~~~~~~~~~~~~ + +For v1 encryption policies, a master encryption key can also be +provided by adding it to a process-subscribed keyring, e.g. to a +session keyring, or to a user keyring if the user keyring is linked +into the session keyring. + +This method is deprecated (and not supported for v2 encryption +policies) for several reasons. First, it cannot be used in +combination with FS_IOC_REMOVE_ENCRYPTION_KEY (see `Removing keys`_), +so for removing a key a workaround such as keyctl_unlink() in +combination with ``sync; echo 2 > /proc/sys/vm/drop_caches`` would +have to be used. Second, it doesn't match the fact that the +locked/unlocked status of encrypted files (i.e. whether they appear to +be in plaintext form or in ciphertext form) is global. This mismatch +has caused much confusion as well as real problems when processes +running under different UIDs, such as a ``sudo`` command, need to +access encrypted files. + +Nevertheless, to add a key to one of the process-subscribed keyrings, +the add_key() system call can be used (see: ``Documentation/security/keys/core.rst``). The key type must be "logon"; keys of this type are kept in kernel memory and cannot be read back by userspace. The key description must be "fscrypt:" @@ -399,12 +685,12 @@ followed by the 16-character lower case hex representation of the ``master_key_descriptor`` that was set in the encryption policy. The key payload must conform to the following structure:: - #define FSCRYPT_MAX_KEY_SIZE 64 + #define FSCRYPT_MAX_KEY_SIZE 64 struct fscrypt_key { - u32 mode; - u8 raw[FSCRYPT_MAX_KEY_SIZE]; - u32 size; + __u32 mode; + __u8 raw[FSCRYPT_MAX_KEY_SIZE]; + __u32 size; }; ``mode`` is ignored; just set it to 0. The actual key is provided in @@ -416,26 +702,145 @@ with a filesystem-specific prefix such as "ext4:". However, the filesystem-specific prefixes are deprecated and should not be used in new programs. -There are several different types of keyrings in which encryption keys -may be placed, such as a session keyring, a user session keyring, or a -user keyring. Each key must be placed in a keyring that is "attached" -to all processes that might need to access files encrypted with it, in -the sense that request_key() will find the key. Generally, if only -processes belonging to a specific user need to access a given -encrypted directory and no session keyring has been installed, then -that directory's key should be placed in that user's user session -keyring or user keyring. Otherwise, a session keyring should be -installed if needed, and the key should be linked into that session -keyring, or in a keyring linked into that session keyring. - -Note: introducing the complex visibility semantics of keyrings here -was arguably a mistake --- especially given that by design, after any -process successfully opens an encrypted file (thereby setting up the -per-file key), possessing the keyring key is not actually required for -any process to read/write the file until its in-memory inode is -evicted. In the future there probably should be a way to provide keys -directly to the filesystem instead, which would make the intended -semantics clearer. +Removing keys +------------- + +The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl can be used to remove a master +encryption key from the kernel, wiping the corresponding secrets from +memory and causing any files which were "unlocked" with the key to +appear "locked" again. It can be executed on any file or directory on +the target filesystem, but using the filesystem's root directory is +recommended. It takes in a pointer to a :c:type:`struct +fscrypt_remove_key_arg`, defined as follows:: + + struct fscrypt_remove_key_arg { + struct fscrypt_key_specifier key_spec; + #define FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS 0x00000001 + __u32 flags; + __u32 __reserved[5]; + }; + +This structure must be zeroed, then initialized as follows: + +- The key to remove is specified by ``key_spec``: + + - To remove a key used by v1 encryption policies, set + ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill + in ``key_spec.u.descriptor``. To remove this type of key, the + calling process must have the CAP_SYS_ADMIN capability in the + initial user namespace. + + - To remove a key used by v2 encryption policies, set + ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill + in ``key_spec.u.identifier``. To remove this type of key, no + privileges are needed. However, users can only remove keys that + they added themselves, subject to privileged override with + FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS. + +- ``flags`` can contain the following flags: + + - ``FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS`` specifies that the key + should be removed even if it has also been added by other users. + Specifying this flag requires the CAP_SYS_ADMIN capability in + the initial user namespace. + +FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors: + +- ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type + and/or the FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS flag was specified, but + the caller does not have the CAP_SYS_ADMIN capability in the initial + user namespace +- ``EBUSY``: the master key secret was wiped from memory, but some + files which were unlocked with it are still in use. Such files + could not be locked, nor could their per-file keys be wiped from + memory. The ioctl may be retried later to re-attempt locking the + remaining files. Note: if the files cease being used, the key + removal may (but is not guaranteed to) complete before this ioctl is + retried; in this case, retrying this ioctl will return ``ENOKEY``. +- ``EINVAL``: invalid flags or key specifier type, or reserved bits + were set +- ``ENOKEY``: the key is not present or has already been fully removed +- ``ENOTTY``: this type of filesystem does not implement encryption +- ``EOPNOTSUPP``: the kernel was not configured with encryption + support for this filesystem, or the filesystem superblock has not + had encryption enabled on it +- ``EUSERS``: the key cannot be removed because other users have added + it too + +Before using this ioctl, read the `Kernel memory compromise`_ section +for a discussion of the security goals and limitations of this ioctl. + +Getting key status +------------------ + +The FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl retrieves the status of a +master encryption key. It can be executed on any file or directory on +the target filesystem, but using the filesystem's root directory is +recommended. It takes in a pointer to a :c:type:`struct +fscrypt_get_key_status_arg`, defined as follows:: + + struct fscrypt_get_key_status_arg { + /* input */ + struct fscrypt_key_specifier key_spec; + __u32 __reserved[6]; + + /* output */ + #define FSCRYPT_KEY_STATUS_ABSENT 1 + #define FSCRYPT_KEY_STATUS_PRESENT 2 + #define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED 3 + __u32 status; + #define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF 0x00000001 + __u32 status_flags; + __u32 user_count; + __u32 __out_reserved[13]; + }; + +The caller must zero all input fields, then fill in ``key_spec``: + + - To get the status of a key for v1 encryption policies, set + ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill + in ``key_spec.u.descriptor``. + + - To get the status of a key for v2 encryption policies, set + ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill + in ``key_spec.u.identifier``. + +On success, 0 is returned and the kernel fills in the output fields: + +- ``status`` indicates whether the key is absent, present, or + incompletely removed. Incompletely removed means that the master + secret has been removed, but some files are still in use; i.e., + FS_IOC_REMOVE_ENCRYPTION_KEY returned EBUSY. + +- ``status_flags`` can contain the following flags: + + - ``FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF`` indicates that the key + has added by the current user. This is only set for keys + identified by ``identifier`` rather than by ``descriptor``. + +- ``user_count`` specifies the number of users who have added the key. + This is only set for keys identified by ``identifier`` rather than + by ``descriptor``. + +FS_IOC_GET_ENCRYPTION_KEY_STATUS can fail with the following errors: + +- ``EINVAL``: invalid key specifier type, or reserved bits were set +- ``ENOTTY``: this type of filesystem does not implement encryption +- ``EOPNOTSUPP``: the kernel was not configured with encryption + support for this filesystem, or the filesystem superblock has not + had encryption enabled on it + +Among other use cases, FS_IOC_GET_ENCRYPTION_KEY_STATUS might be +useful for determining whether the key for a given encrypted directory +needs to be added before prompting the user for the passphrase needed +to derive the key. + +FS_IOC_GET_ENCRYPTION_KEY_STATUS can only get the status of keys in +the filesystem-level keyring, i.e. the keyring managed by +FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY. It cannot +get the status of a key that has only been added for use by v1 +encryption policies using the legacy mechanism involving +process-subscribed keyrings. Access semantics ================ @@ -498,7 +903,7 @@ Without the key Some filesystem operations may be performed on encrypted regular files, directories, and symlinks even before their encryption key has -been provided: +been added, or after their encryption key has been removed: - File metadata may be read, e.g. using stat(). @@ -563,20 +968,20 @@ Encryption context ------------------ An encryption policy is represented on-disk by a :c:type:`struct -fscrypt_context`. It is up to individual filesystems to decide where -to store it, but normally it would be stored in a hidden extended -attribute. It should *not* be exposed by the xattr-related system -calls such as getxattr() and setxattr() because of the special -semantics of the encryption xattr. (In particular, there would be -much confusion if an encryption policy were to be added to or removed -from anything other than an empty directory.) The struct is defined -as follows:: +fscrypt_context_v1` or a :c:type:`struct fscrypt_context_v2`. It is +up to individual filesystems to decide where to store it, but normally +it would be stored in a hidden extended attribute. It should *not* be +exposed by the xattr-related system calls such as getxattr() and +setxattr() because of the special semantics of the encryption xattr. +(In particular, there would be much confusion if an encryption policy +were to be added to or removed from anything other than an empty +directory.) These structs are defined as follows:: - #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 #define FS_KEY_DERIVATION_NONCE_SIZE 16 - struct fscrypt_context { - u8 format; + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8 + struct fscrypt_context_v1 { + u8 version; u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; @@ -584,12 +989,23 @@ as follows:: u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; -Note that :c:type:`struct fscrypt_context` contains the same -information as :c:type:`struct fscrypt_policy` (see `Setting an -encryption policy`_), except that :c:type:`struct fscrypt_context` -also contains a nonce. The nonce is randomly generated by the kernel -and is used to derive the inode's encryption key as described in -`Per-file keys`_. + #define FSCRYPT_KEY_IDENTIFIER_SIZE 16 + struct fscrypt_context_v2 { + u8 version; + u8 contents_encryption_mode; + u8 filenames_encryption_mode; + u8 flags; + u8 __reserved[4]; + u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; + }; + +The context structs contain the same information as the corresponding +policy structs (see `Setting an encryption policy`_), except that the +context structs also contain a nonce. The nonce is randomly generated +by the kernel and is used as KDF input or as a tweak to cause +different files to be encrypted differently; see `Per-file keys`_ and +`DIRECT_KEY and per-mode keys`_. Data path changes -----------------